Granzyme B: Difference between revisions
→Nucleus: edited typo |
m Journal cites, added 1 PMC using AWB (10484) |
||
| Line 23: | Line 23: | ||
Granzyme B's structure consists of two 6 stranded [[β sheets]] with 3 trans domain segments. In the granules of cytotoxic lymphocytes the enzyme can exist in two [[glycosylation|glycosylated]] forms. The high mannose form weighs 32kDa and the complex form, 35kDa.<ref name="Rousalova2010">{{cite journal | title= Granzyme B-induced apoptosis in cancer cells and its regulation (review) | author = Rousalova I | year = 2010 | pmid= 21042704 | volume=37 | issue=6 | journal=Int. J. Oncol. | pages=1361–78}}</ref> |
Granzyme B's structure consists of two 6 stranded [[β sheets]] with 3 trans domain segments. In the granules of cytotoxic lymphocytes the enzyme can exist in two [[glycosylation|glycosylated]] forms. The high mannose form weighs 32kDa and the complex form, 35kDa.<ref name="Rousalova2010">{{cite journal | title= Granzyme B-induced apoptosis in cancer cells and its regulation (review) | author = Rousalova I | year = 2010 | pmid= 21042704 | volume=37 | issue=6 | journal=Int. J. Oncol. | pages=1361–78}}</ref> |
||
Granzyme B contains the [[catalytic triad]] [[histidine]]-[[aspartic acid]]-[[serine]] in its [[active site]] and preferentially cleaves after an [[aspartic acid]] residue situated in the P1 position. The aspartic acid residue to be cleaved associates with an [[arginine]] residue in the enzyme's binding pocket.<ref name="Boivin2009">{{ cite journal | title = Intracellular versus extracellular granzyme B in immunity and disease: challenging the dogma | author= Boivin WA | year= 2009 | pmid= 19770840 | doi= 10.1038/labinvest.2009.91 | volume=89 | issue=11}}</ref> |
Granzyme B contains the [[catalytic triad]] [[histidine]]-[[aspartic acid]]-[[serine]] in its [[active site]] and preferentially cleaves after an [[aspartic acid]] residue situated in the P1 position. The aspartic acid residue to be cleaved associates with an [[arginine]] residue in the enzyme's binding pocket.<ref name="Boivin2009">{{ cite journal | title = Intracellular versus extracellular granzyme B in immunity and disease: challenging the dogma | author= Boivin WA | year= 2009 | pmid= 19770840 | doi= 10.1038/labinvest.2009.91 | volume=89 | issue=11 | pages=1195–220}}</ref> |
||
Granzyme B is active at a neutral [[pH]] and is therefore inactive in the acidic CTL granules. The enzyme is also rendered inactive when bound by [[SRGN|serglycin]] in the granules to avoid apoptosis triggering inside the cytotoxic T cells themselves.<ref name="Wowk">{{ cite journal | title= Cytotoxic activity of the lymphocyte toxin granzyme B | author= Wowk ME | year= 2004 | pmid= 15207822 | doi=10.1016/j.micinf.2004.03.008 | volume=6 | issue=8 | journal=Microbes Infect. | pages=752–8}}</ref> |
Granzyme B is active at a neutral [[pH]] and is therefore inactive in the acidic CTL granules. The enzyme is also rendered inactive when bound by [[SRGN|serglycin]] in the granules to avoid apoptosis triggering inside the cytotoxic T cells themselves.<ref name="Wowk">{{ cite journal | title= Cytotoxic activity of the lymphocyte toxin granzyme B | author= Wowk ME | year= 2004 | pmid= 15207822 | doi=10.1016/j.micinf.2004.03.008 | volume=6 | issue=8 | journal=Microbes Infect. | pages=752–8}}</ref> |
||
| Line 29: | Line 29: | ||
Granzyme B is released with perforin which inserts into a target cell's [[plasma membrane]] forming a [[pore]]. Perforin has a radius of 5.5 nm and granzyme B has a [[stokes radius]] of 2.5 nm and can therefore pass through the perforin pore into the target to be destroyed. |
Granzyme B is released with perforin which inserts into a target cell's [[plasma membrane]] forming a [[pore]]. Perforin has a radius of 5.5 nm and granzyme B has a [[stokes radius]] of 2.5 nm and can therefore pass through the perforin pore into the target to be destroyed. |
||
Alternatively, once released, granzyme B can bind to negatively charged [[heparan sulphate]] containing receptors on a target cell and become [[endocytosis|endocytosed]]. The [[Vesicle (biology and chemistry)|vesicles]] that carry the enzyme inside then burst, exposing granzyme b to the [[cytoplasm]] and its [[substrate (biochemistry)|substrates]].<ref name="Kurschus2012" /> [[Hsp70|Hsp-70]] has also been linked to aiding granzyme B entry.<ref name="Boivin2009">{{ cite journal | title = Intracellular versus extracellular granzyme B in immunity and disease: challenging the dogma | author= Boivin WA | year= 2009 | pmid= 19770840 | doi= 10.1038/labinvest.2009.91 | volume=89 | issue=11}}</ref><ref name="Cullen2010">{{ cite journal | title = Granzymes in cancer and immunity | author = Cullen SP | year = 2010 | pmid= 20075940 | doi= 10.1038/cdd.2009.206 | volume=17 | issue=4}}</ref> |
Alternatively, once released, granzyme B can bind to negatively charged [[heparan sulphate]] containing receptors on a target cell and become [[endocytosis|endocytosed]]. The [[Vesicle (biology and chemistry)|vesicles]] that carry the enzyme inside then burst, exposing granzyme b to the [[cytoplasm]] and its [[substrate (biochemistry)|substrates]].<ref name="Kurschus2012" /> [[Hsp70|Hsp-70]] has also been linked to aiding granzyme B entry.<ref name="Boivin2009">{{ cite journal | title = Intracellular versus extracellular granzyme B in immunity and disease: challenging the dogma | author= Boivin WA | year= 2009 | pmid= 19770840 | doi= 10.1038/labinvest.2009.91 | volume=89 | issue=11 | pages=1195–220}}</ref><ref name="Cullen2010">{{ cite journal | title = Granzymes in cancer and immunity | author = Cullen SP | year = 2010 | pmid= 20075940 | doi= 10.1038/cdd.2009.206 | volume=17 | issue=4 | pages=616–23}}</ref> |
||
Granzyme B has also been proposed to enter a target by first exchanging its bound serglycin for negative [[phospholipids]] in a target's plasma membrane. Entry then occurs by the less selective process of [[pinocytosis|absorptive pinocytosis]].<ref name="Rousalova2010">{{cite journal | title= Granzyme B-induced apoptosis in cancer cells and its regulation (review) | author = Rousalova I | year = 2010 | pmid= 21042704 | volume=37 | issue=6 | journal=Int. J. Oncol. | pages=1361–78}}</ref> |
Granzyme B has also been proposed to enter a target by first exchanging its bound serglycin for negative [[phospholipids]] in a target's plasma membrane. Entry then occurs by the less selective process of [[pinocytosis|absorptive pinocytosis]].<ref name="Rousalova2010">{{cite journal | title= Granzyme B-induced apoptosis in cancer cells and its regulation (review) | author = Rousalova I | year = 2010 | pmid= 21042704 | volume=37 | issue=6 | journal=Int. J. Oncol. | pages=1361–78}}</ref> |
||
| Line 40: | Line 40: | ||
Granzyme B has a potential of over 300 substrates and can cleave [[Mcl-1]] in the [[outer mitochondrial membrane]] relieving its inhibition of [[BCL2L11|Bim]]. Bim stimulates BAX/BAK oligomerisation, mitochondrial membrane permeability and apoptosis. Granzyme B can also cleave [[HAX1]] (Hs-1 associated protein X-1) to facilitate mitochondria polarisation.<ref name="Rousalova2010">{{cite journal | title= Granzyme B-induced apoptosis in cancer cells and its regulation (review) | author = Rousalova I | year = 2010 | pmid= 21042704 | volume=37 | issue=6 | journal=Int. J. Oncol. | pages=1361–78}}</ref> |
Granzyme B has a potential of over 300 substrates and can cleave [[Mcl-1]] in the [[outer mitochondrial membrane]] relieving its inhibition of [[BCL2L11|Bim]]. Bim stimulates BAX/BAK oligomerisation, mitochondrial membrane permeability and apoptosis. Granzyme B can also cleave [[HAX1]] (Hs-1 associated protein X-1) to facilitate mitochondria polarisation.<ref name="Rousalova2010">{{cite journal | title= Granzyme B-induced apoptosis in cancer cells and its regulation (review) | author = Rousalova I | year = 2010 | pmid= 21042704 | volume=37 | issue=6 | journal=Int. J. Oncol. | pages=1361–78}}</ref> |
||
Granzyme B can also generate a cytotoxic level of mitochondrial [[reactive oxygen species]] (ROS) to mediate cell death.<ref name="Choy2010">{{ cite journal | title = Granzymes and perforin in solid organ transplant rejection | author = Choy JC | year = 2010 | pmid= 19876069 | doi= 10.1038/cdd.2009.161 | volume=17 | issue=4}}</ref> The caspase independent pathways of cell death are thought to have arisen to overcome [[viruses]] that can inhibit caspases and prevent apoptosis.<ref name="Wowk">{{ cite journal | title= Cytotoxic activity of the lymphocyte toxin granzyme B | author= Wowk ME | year= 2004 | pmid= 15207822 | doi=10.1016/j.micinf.2004.03.008 | volume=6 | issue=8 | journal=Microbes Infect. | pages=752–8}}</ref> |
Granzyme B can also generate a cytotoxic level of mitochondrial [[reactive oxygen species]] (ROS) to mediate cell death.<ref name="Choy2010">{{ cite journal | title = Granzymes and perforin in solid organ transplant rejection | author = Choy JC | year = 2010 | pmid= 19876069 | doi= 10.1038/cdd.2009.161 | volume=17 | issue=4 | pages=567–76}}</ref> The caspase independent pathways of cell death are thought to have arisen to overcome [[viruses]] that can inhibit caspases and prevent apoptosis.<ref name="Wowk">{{ cite journal | title= Cytotoxic activity of the lymphocyte toxin granzyme B | author= Wowk ME | year= 2004 | pmid= 15207822 | doi=10.1016/j.micinf.2004.03.008 | volume=6 | issue=8 | journal=Microbes Infect. | pages=752–8}}</ref> |
||
==Targets== |
==Targets== |
||
| Line 52: | Line 52: | ||
===Extracellular Matrix=== |
===Extracellular Matrix=== |
||
Granzyme B can degrade many proteins in the extracellular matrix (ECM) including [[fibronectin]], [[vitronectin]] and [[aggrecan]]. Cleavage can cause cell death by [[anoikis]] and release alarmins from the ECM inducing inflammation.<ref name="Afonina2010" /> Fragments of fibronectin can attract [[neutrophils]] and stimulate [[Matrix metalloproteinase|MMP]] expression from [[chondrocytes]].<ref name="Boivin2009">{{cite journal| title = Intracellular versus extracellular granzyme B in immunity and disease: challenging the dogma | author= Boivin WA | year= 2009 | pmid= 19770840 | doi= 10.1038/labinvest.2009.91 | volume=89 | issue=11}}</ref> Basophils secrete granzyme B to degrade [[endothelium|endothelial]] cell-cell contacts allowing [[extravasation]] to sites of inflammation.<ref name="Cullen2010">{{ cite journal | title = Granzymes in cancer and immunity | author = Cullen SP | year = 2010 | pmid= 20075940 | doi= 10.1038/cdd.2009.206 | volume=17 | issue=4}}</ref> |
Granzyme B can degrade many proteins in the extracellular matrix (ECM) including [[fibronectin]], [[vitronectin]] and [[aggrecan]]. Cleavage can cause cell death by [[anoikis]] and release alarmins from the ECM inducing inflammation.<ref name="Afonina2010" /> Fragments of fibronectin can attract [[neutrophils]] and stimulate [[Matrix metalloproteinase|MMP]] expression from [[chondrocytes]].<ref name="Boivin2009">{{cite journal| title = Intracellular versus extracellular granzyme B in immunity and disease: challenging the dogma | author= Boivin WA | year= 2009 | pmid= 19770840 | doi= 10.1038/labinvest.2009.91 | volume=89 | issue=11 | pages=1195–220}}</ref> Basophils secrete granzyme B to degrade [[endothelium|endothelial]] cell-cell contacts allowing [[extravasation]] to sites of inflammation.<ref name="Cullen2010">{{ cite journal | title = Granzymes in cancer and immunity | author = Cullen SP | year = 2010 | pmid= 20075940 | doi= 10.1038/cdd.2009.206 | volume=17 | issue=4 | pages=616–23}}</ref> |
||
Granzyme B can also induce inflammation by processing cytokines [[IL1B|IL-1β]] and [[Interleukin 18|IL18]] and by processing [[IL1A|IL-1α]] into a more inflammatory fragment. It can also trigger the release of [[Interleukin 6|IL6]] and [[Interleukin 8|IL8]] through activation of [[Coagulation factor II receptor|PAR1]] (Protease activated receptor 1).<ref name="Hiebert2012">{{ cite journal | title = Granzyme B in injury, inflammation, and repair | author = Hiebert PR | year = 2012 | pmid= 23099058 | doi= 10.1016/j.molmed.2012.09.009 | volume=18 | issue=12 | journal=Trends Mol Med | pages=732–41}}</ref> |
Granzyme B can also induce inflammation by processing cytokines [[IL1B|IL-1β]] and [[Interleukin 18|IL18]] and by processing [[IL1A|IL-1α]] into a more inflammatory fragment. It can also trigger the release of [[Interleukin 6|IL6]] and [[Interleukin 8|IL8]] through activation of [[Coagulation factor II receptor|PAR1]] (Protease activated receptor 1).<ref name="Hiebert2012">{{ cite journal | title = Granzyme B in injury, inflammation, and repair | author = Hiebert PR | year = 2012 | pmid= 23099058 | doi= 10.1016/j.molmed.2012.09.009 | volume=18 | issue=12 | journal=Trends Mol Med | pages=732–41}}</ref> |
||
| Line 67: | Line 67: | ||
Granzyme B's most common inhibitor is [[SERPINB9]] also known as proteinase inhibitor nine (PI-9) which is 376 amino acids long and found in the nucleus and cytoplasm.<ref name="Rousalova2010">{{cite journal | title= Granzyme B-induced apoptosis in cancer cells and its regulation (review) | author = Rousalova I | year = 2010 | pmid= 21042704 | volume=37 | issue=6 | journal=Int. J. Oncol. | pages=1361–78}}</ref> |
Granzyme B's most common inhibitor is [[SERPINB9]] also known as proteinase inhibitor nine (PI-9) which is 376 amino acids long and found in the nucleus and cytoplasm.<ref name="Rousalova2010">{{cite journal | title= Granzyme B-induced apoptosis in cancer cells and its regulation (review) | author = Rousalova I | year = 2010 | pmid= 21042704 | volume=37 | issue=6 | journal=Int. J. Oncol. | pages=1361–78}}</ref> |
||
It is produced by many types of cell to protect themselves from accidental granzyme B mediated cell death. PI-9 is [[metastability|metastable]] and forms an energetically favourable conformation when bound to granzyme B. The reactive loop centre (RCL) of the PI-9 molecule acts as a pseudosubstrate and initially forms a reversible Michaelis complex. Once the [[peptide bond]] of the RCL is cleaved between positions P1 and P1', granzyme B is permanently inhibited. |
It is produced by many types of cell to protect themselves from accidental granzyme B mediated cell death. PI-9 is [[metastability|metastable]] and forms an energetically favourable conformation when bound to granzyme B. The reactive loop centre (RCL) of the PI-9 molecule acts as a pseudosubstrate and initially forms a reversible Michaelis complex. Once the [[peptide bond]] of the RCL is cleaved between positions P1 and P1', granzyme B is permanently inhibited. |
||
However if the RCL is cleaved efficiently, PI-9 does not act as a 1:1 [[suicide inhibition|suicide substrate]] and granzyme B is left uninhibited.<ref name="Kaiserman2010">{{ cite journal | title = Control of granzymes by serpins | author = Kaiserman D | year = 2010 | pmid= 19893573 | doi= 10.1038/cdd.2009.169 | volume=17 | issue=4}}</ref> [[GZMM|Granzyme M]] can also cleave PI-9 in the nucleus and cytoplasm to relieve granzyme B of inhibition.<ref name="Rousalova2010">{{cite journal | title= Granzyme B-induced apoptosis in cancer cells and its regulation (review) | author = Rousalova I | year = 2010 | pmid= 21042704 | volume=37 | issue=6 | journal=Int. J. Oncol. | pages=1361–78}}</ref> |
However if the RCL is cleaved efficiently, PI-9 does not act as a 1:1 [[suicide inhibition|suicide substrate]] and granzyme B is left uninhibited.<ref name="Kaiserman2010">{{ cite journal | title = Control of granzymes by serpins | author = Kaiserman D | year = 2010 | pmid= 19893573 | doi= 10.1038/cdd.2009.169 | volume=17 | issue=4 | pages=586–95}}</ref> [[GZMM|Granzyme M]] can also cleave PI-9 in the nucleus and cytoplasm to relieve granzyme B of inhibition.<ref name="Rousalova2010">{{cite journal | title= Granzyme B-induced apoptosis in cancer cells and its regulation (review) | author = Rousalova I | year = 2010 | pmid= 21042704 | volume=37 | issue=6 | journal=Int. J. Oncol. | pages=1361–78}}</ref> |
||
Protein L4-100K from [[adenoviridae|adenoviruses]] can also inhibit granzyme B by binding at [[exosite]]s and specific binding pockets.<ref name="Kurschus2012" /> L4-100K is an assembly protein that can transport [[capsomere|hexon capsomeres]] into the nucleus of an adenovirus. 100k can be cleaved to a 90kDa fragment by [[granzyme H]] to relieve this inhibition which is important in adenovirus 5 infected cells.<ref name="Waterhouse2007">{{ cite journal | title = H is for helper: granzyme H helps granzyme B kill adenovirus-infected cells | author = Waterhouse NJ | year = 2007 | pmid= 17766182 | doi=10.1016/j.it.2007.08.001 | volume=28 | issue=9 | pages=373–5}}</ref> |
Protein L4-100K from [[adenoviridae|adenoviruses]] can also inhibit granzyme B by binding at [[exosite]]s and specific binding pockets.<ref name="Kurschus2012" /> L4-100K is an assembly protein that can transport [[capsomere|hexon capsomeres]] into the nucleus of an adenovirus. 100k can be cleaved to a 90kDa fragment by [[granzyme H]] to relieve this inhibition which is important in adenovirus 5 infected cells.<ref name="Waterhouse2007">{{ cite journal | title = H is for helper: granzyme H helps granzyme B kill adenovirus-infected cells | author = Waterhouse NJ | year = 2007 | pmid= 17766182 | doi=10.1016/j.it.2007.08.001 | volume=28 | issue=9 | pages=373–5}}</ref> |
||
| Line 73: | Line 73: | ||
==Role in Disease== |
==Role in Disease== |
||
Granzyme B has a normal concentration of 20-4-pg/ml in the [[blood plasma]] while retaining 70% activity and elevated concentrations of granzyme B are found in a number of disease states.<ref name="Boivin2009">{{ cite journal | title = Intracellular versus extracellular granzyme B in immunity and disease: challenging the dogma | author= Boivin WA | year= 2009 | pmid= 19770840 | doi= 10.1038/labinvest.2009.91 | volume=89 | issue=11}}</ref> |
Granzyme B has a normal concentration of 20-4-pg/ml in the [[blood plasma]] while retaining 70% activity and elevated concentrations of granzyme B are found in a number of disease states.<ref name="Boivin2009">{{ cite journal | title = Intracellular versus extracellular granzyme B in immunity and disease: challenging the dogma | author= Boivin WA | year= 2009 | pmid= 19770840 | doi= 10.1038/labinvest.2009.91 | volume=89 | issue=11 | pages=1195–220}}</ref> |
||
Granzyme B can generate autoantigens by cleaving in disordered regions and linker regions of antigens exposing new [[epitopes]] and this can cause the development of autoimmune diseases.<ref name="Boivin2009">{{ cite journal | title = Intracellular versus extracellular granzyme B in immunity and disease: challenging the dogma | author= Boivin WA | year= 2009 | pmid= 19770840 | doi= 10.1038/labinvest.2009.91 | volume=89 | issue=11}}</ref><ref name="Darrah2010">{{ cite journal | title = Granzyme B cleavage of autoantigens in autoimmunity | author = Darrah E | year = 2010 | pmid= 20075942 | doi= 10.1038/cdd.2009.197 | volume=17 | issue=4}}</ref> |
Granzyme B can generate autoantigens by cleaving in disordered regions and linker regions of antigens exposing new [[epitopes]] and this can cause the development of autoimmune diseases.<ref name="Boivin2009">{{ cite journal | title = Intracellular versus extracellular granzyme B in immunity and disease: challenging the dogma | author= Boivin WA | year= 2009 | pmid= 19770840 | doi= 10.1038/labinvest.2009.91 | volume=89 | issue=11 | pages=1195–220}}</ref><ref name="Darrah2010">{{ cite journal | title = Granzyme B cleavage of autoantigens in autoimmunity | author = Darrah E | year = 2010 | pmid= 20075942 | doi= 10.1038/cdd.2009.197 | volume=17 | issue=4 | pmc=3136751 | pages=624–32}}</ref> |
||
Granzyme B release with perforin from [[CD8]] T cells can cause [[heart]] and [[kidney]] [[transplant rejection]] through killing of allogeneic endothelial cells. The destruction of [[insulin]] producing [[beta cell|β cells]] in [[islets of Langerhans|pancreatic islets]] is mediated by T cells and granzyme B contributing to Type 1 Diabetes. Granzyme B can also mediate the death of cells after [[spinal cord injury]] and is found at elevated levels in [[rheumatoid arthritis]]. |
Granzyme B release with perforin from [[CD8]] T cells can cause [[heart]] and [[kidney]] [[transplant rejection]] through killing of allogeneic endothelial cells. The destruction of [[insulin]] producing [[beta cell|β cells]] in [[islets of Langerhans|pancreatic islets]] is mediated by T cells and granzyme B contributing to Type 1 Diabetes. Granzyme B can also mediate the death of cells after [[spinal cord injury]] and is found at elevated levels in [[rheumatoid arthritis]]. |
||
| Line 81: | Line 81: | ||
Granzyme B can kill [[melanocytes]] causing the skin condition [[vitiligo]] and granzyme B overexpression is found in [[contact dermatitis]], [[lichen sclerosus]] and [[lichen planus]] cases. |
Granzyme B can kill [[melanocytes]] causing the skin condition [[vitiligo]] and granzyme B overexpression is found in [[contact dermatitis]], [[lichen sclerosus]] and [[lichen planus]] cases. |
||
Cytotoxic cells expressing granzyme B have been identified close to [[hair follicles]] linking a possible role in hair loss.<ref name="Boivin2009">{{ cite journal | title = Intracellular versus extracellular granzyme B in immunity and disease: challenging the dogma | author= Boivin WA | year= 2009 | pmid= 19770840 | doi= 10.1038/labinvest.2009.91 | volume=89 | issue=11}}</ref> |
Cytotoxic cells expressing granzyme B have been identified close to [[hair follicles]] linking a possible role in hair loss.<ref name="Boivin2009">{{ cite journal | title = Intracellular versus extracellular granzyme B in immunity and disease: challenging the dogma | author= Boivin WA | year= 2009 | pmid= 19770840 | doi= 10.1038/labinvest.2009.91 | volume=89 | issue=11 | pages=1195–220}}</ref> |
||
The ECM remodelling properties of granzyme B have also implicated its involvement in [[ventricular remodeling|left ventricular remodelling]], which increases the subsequent chances of [[myocardial infarction]]. The weakening of the [[fibrous cap]] of [[atheroma| atheromatous plaques]] by apoptosis of smooth muscle cells has also been linked to granzyme B.<ref name="Saito2011">{{ cite journal | title = Granzyme B as a noverl factor involed in cardiovascular diseases | author = Saito Y | year = 2011 | pmid = 21168312 | doi = 10.1016/j.jjcc.2010.10.001 | volume=57 | issue=2 | journal=J Cardiol | pages=141–7}}</ref> |
The ECM remodelling properties of granzyme B have also implicated its involvement in [[ventricular remodeling|left ventricular remodelling]], which increases the subsequent chances of [[myocardial infarction]]. The weakening of the [[fibrous cap]] of [[atheroma| atheromatous plaques]] by apoptosis of smooth muscle cells has also been linked to granzyme B.<ref name="Saito2011">{{ cite journal | title = Granzyme B as a noverl factor involed in cardiovascular diseases | author = Saito Y | year = 2011 | pmid = 21168312 | doi = 10.1016/j.jjcc.2010.10.001 | volume=57 | issue=2 | journal=J Cardiol | pages=141–7}}</ref> |
||
Revision as of 20:43, 9 November 2014
| Granzyme B | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Identifiers | |||||||||
| EC no. | 3.4.21.79 | ||||||||
| CAS no. | 143180-74-9 | ||||||||
| Databases | |||||||||
| IntEnz | IntEnz view | ||||||||
| BRENDA | BRENDA entry | ||||||||
| ExPASy | NiceZyme view | ||||||||
| KEGG | KEGG entry | ||||||||
| MetaCyc | metabolic pathway | ||||||||
| PRIAM | profile | ||||||||
| PDB structures | RCSB PDB PDBe PDBsum | ||||||||
| |||||||||
Granzyme B is a serine protease most commonly found in the granules of cytotoxic lymphocytes (CTLs), natural killer cells (NK cells) and cytotoxic T cells. It is secreted by these cells along with the pore forming protein perforin to mediate apoptosis in target cells.
Granzyme B has also more recently found to be produced by a wide range of non-cytotoxic cells ranging from basophils and mast cells to smooth muscle cells.[1] The secondary functions of granzyme B are also numerous. Granzyme B has shown to be involved in inducing inflammation by stimulating cytokine release and is also involved in extracellular matrix remodelling.
Elevated levels of granzyme B are also implicated in a number of autoimmune diseases, several skin diseases, and type 1 diabetes.
Structure
Granzyme B is encoded by GZMB on chromosome 14q.11.2 which is 3.2kb long consisting of 4 introns and 5 exons.[2] It is one of the most abundant granzymes of which there are 5 in humans and 10 in mice.[1] Granzyme B is thought to have evolved from a granzyme H related precursor and is more effective at lower concentrations than the other granzymes.[3]
The enzyme is initially in an inactive precursor zymogen form, with an additional amino terminal peptide sequence.[3] This sequence can be cleaved by cathepsin c, removing 2 amino acids.[4] Cathepsin H has also been reported to activate granzyme B.[2]
Granzyme B's structure consists of two 6 stranded β sheets with 3 trans domain segments. In the granules of cytotoxic lymphocytes the enzyme can exist in two glycosylated forms. The high mannose form weighs 32kDa and the complex form, 35kDa.[2]
Granzyme B contains the catalytic triad histidine-aspartic acid-serine in its active site and preferentially cleaves after an aspartic acid residue situated in the P1 position. The aspartic acid residue to be cleaved associates with an arginine residue in the enzyme's binding pocket.[5] Granzyme B is active at a neutral pH and is therefore inactive in the acidic CTL granules. The enzyme is also rendered inactive when bound by serglycin in the granules to avoid apoptosis triggering inside the cytotoxic T cells themselves.[4]
Delivery
Granzyme B is released with perforin which inserts into a target cell's plasma membrane forming a pore. Perforin has a radius of 5.5 nm and granzyme B has a stokes radius of 2.5 nm and can therefore pass through the perforin pore into the target to be destroyed.
Alternatively, once released, granzyme B can bind to negatively charged heparan sulphate containing receptors on a target cell and become endocytosed. The vesicles that carry the enzyme inside then burst, exposing granzyme b to the cytoplasm and its substrates.[3] Hsp-70 has also been linked to aiding granzyme B entry.[5][6]
Granzyme B has also been proposed to enter a target by first exchanging its bound serglycin for negative phospholipids in a target's plasma membrane. Entry then occurs by the less selective process of absorptive pinocytosis.[2]
Granzyme B Mediated Apoptosis
Once inside the target cell granzyme B can cleave and activate initiator caspases 8 and 10, and executioner caspases 3 and 7 which trigger apoptosis.[1] Caspase 7 is the most sensitive to granzyme B and caspases 3, 8, and 10 are only cleaved to intermediate fragments and need further cleavage for full activation.[7]
Granzyme B can also cleave BID leading to BAX/BAK oligomerisation and cytochrome c release from the mitochondria. Granzyme B can cleave ICAD leading to DNA fragmentation and the laddering pattern associated with apoptosis.[1]
Granzyme B has a potential of over 300 substrates and can cleave Mcl-1 in the outer mitochondrial membrane relieving its inhibition of Bim. Bim stimulates BAX/BAK oligomerisation, mitochondrial membrane permeability and apoptosis. Granzyme B can also cleave HAX1 (Hs-1 associated protein X-1) to facilitate mitochondria polarisation.[2]
Granzyme B can also generate a cytotoxic level of mitochondrial reactive oxygen species (ROS) to mediate cell death.[8] The caspase independent pathways of cell death are thought to have arisen to overcome viruses that can inhibit caspases and prevent apoptosis.[4]
Targets
Nucleus
Granzyme B has many substrates located in the nucleus. Granzyme B can cleave PARP (poly ADP ribose polymerase) and DNA PK (DNA protein kinase) to disrupt DNA repair and retroviral DNA integration. Granzyme B can also cleave nucleophosmin, topoisomerase 1 and nucleolin to prevent viral replication.
Granzyme B can cleave ICP4 from the HSV 1 virus which is an essential protein used for gene transactivation and NUMA (Nuclear mitotic apparatus protein) can be cleaved to prevent mitosis.[1]
Granzyme B can also cleave DBP (DNA Binding Protein) into a 50 kDa fragment and then into an additional 60 kDa indirectly through the caspases it activates.[9]
Extracellular Matrix
Granzyme B can degrade many proteins in the extracellular matrix (ECM) including fibronectin, vitronectin and aggrecan. Cleavage can cause cell death by anoikis and release alarmins from the ECM inducing inflammation.[1] Fragments of fibronectin can attract neutrophils and stimulate MMP expression from chondrocytes.[5] Basophils secrete granzyme B to degrade endothelial cell-cell contacts allowing extravasation to sites of inflammation.[6]
Granzyme B can also induce inflammation by processing cytokines IL-1β and IL18 and by processing IL-1α into a more inflammatory fragment. It can also trigger the release of IL6 and IL8 through activation of PAR1 (Protease activated receptor 1).[10]
Cleavage of vitronectin occurs at the RGD integrin binding site interrupting cell growth signalling pathways. Cleavage of laminin and fibronectin disrupts dermal-epidermal junction attachment and cross talk while decorin destruction by granzyme B causes collagen disorganisation, skin thinning and aging. Keratinocytes can express granzyme B after exposure to UVA and UVB which is linked to photoaging of the skin.[10]
Granzyme B can also impair wound healing. Cleavage of the von Willebrand factor inhibits platelet aggregation and of plasminogen produces an angiostatin fragment preventing angiogenesis. The cutting of fibronectins and vitronectins delays the formation of a provisional matrix impairing wound healing further.[10]
T cell Regulation
Granzyme B is secreted by regulatory T cells to kill CD4+ T cells that have not been exposed to host cells that are restricted to the peripheral tissues and cannot reach the thymus. This activation-induced cell death (AICD) can be achieved without the Fas death pathway and prevents autoimmune reaction to self antigens.[1]
Inhibitors
Granzyme B's most common inhibitor is SERPINB9 also known as proteinase inhibitor nine (PI-9) which is 376 amino acids long and found in the nucleus and cytoplasm.[2] It is produced by many types of cell to protect themselves from accidental granzyme B mediated cell death. PI-9 is metastable and forms an energetically favourable conformation when bound to granzyme B. The reactive loop centre (RCL) of the PI-9 molecule acts as a pseudosubstrate and initially forms a reversible Michaelis complex. Once the peptide bond of the RCL is cleaved between positions P1 and P1', granzyme B is permanently inhibited. However if the RCL is cleaved efficiently, PI-9 does not act as a 1:1 suicide substrate and granzyme B is left uninhibited.[11] Granzyme M can also cleave PI-9 in the nucleus and cytoplasm to relieve granzyme B of inhibition.[2]
Protein L4-100K from adenoviruses can also inhibit granzyme B by binding at exosites and specific binding pockets.[3] L4-100K is an assembly protein that can transport hexon capsomeres into the nucleus of an adenovirus. 100k can be cleaved to a 90kDa fragment by granzyme H to relieve this inhibition which is important in adenovirus 5 infected cells.[9]
Role in Disease
Granzyme B has a normal concentration of 20-4-pg/ml in the blood plasma while retaining 70% activity and elevated concentrations of granzyme B are found in a number of disease states.[5] Granzyme B can generate autoantigens by cleaving in disordered regions and linker regions of antigens exposing new epitopes and this can cause the development of autoimmune diseases.[5][12]
Granzyme B release with perforin from CD8 T cells can cause heart and kidney transplant rejection through killing of allogeneic endothelial cells. The destruction of insulin producing β cells in pancreatic islets is mediated by T cells and granzyme B contributing to Type 1 Diabetes. Granzyme B can also mediate the death of cells after spinal cord injury and is found at elevated levels in rheumatoid arthritis.
COPD (Chronic Obstructive Pulmonary Disease) has been attributed to granzyme B secreted from NK and T cells causing the apoptosis of bronchial epithelial cells. Matrix destabilisation and remodelling by granzyme B is also linked to asthma pathogenesis. Granzyme B can kill melanocytes causing the skin condition vitiligo and granzyme B overexpression is found in contact dermatitis, lichen sclerosus and lichen planus cases.
Cytotoxic cells expressing granzyme B have been identified close to hair follicles linking a possible role in hair loss.[5]
The ECM remodelling properties of granzyme B have also implicated its involvement in left ventricular remodelling, which increases the subsequent chances of myocardial infarction. The weakening of the fibrous cap of atheromatous plaques by apoptosis of smooth muscle cells has also been linked to granzyme B.[13]
See also
References
- ^ a b c d e f g Afonina IS (2010). "Cytotoxic and non-cytotoxic roles of the CTL/NK protease granzyme B". Immunol. Rev. 235 (1): 105–16. doi:10.1111/j.0105-2896.2010.00908.x. PMID 20536558.
- ^ a b c d e f g Rousalova I (2010). "Granzyme B-induced apoptosis in cancer cells and its regulation (review)". Int. J. Oncol. 37 (6): 1361–78. PMID 21042704. Cite error: The named reference "Rousalova2010" was defined multiple times with different content (see the help page).
- ^ a b c d Kurschus FC (2010). "Delivery and therapeutic potential of human granzyme B". Immunol. Rev. 235 (1): 159–71. doi:10.1111/j.0105-2896.2010.00894.x. PMID 20536562.
- ^ a b c Wowk ME (2004). "Cytotoxic activity of the lymphocyte toxin granzyme B". Microbes Infect. 6 (8): 752–8. doi:10.1016/j.micinf.2004.03.008. PMID 15207822.
- ^ a b c d e f Boivin WA (2009). "Intracellular versus extracellular granzyme B in immunity and disease: challenging the dogma". 89 (11): 1195–220. doi:10.1038/labinvest.2009.91. PMID 19770840.
{{cite journal}}: Cite journal requires|journal=(help) Cite error: The named reference "Boivin2009" was defined multiple times with different content (see the help page). - ^ a b Cullen SP (2010). "Granzymes in cancer and immunity". 17 (4): 616–23. doi:10.1038/cdd.2009.206. PMID 20075940.
{{cite journal}}: Cite journal requires|journal=(help) - ^ Waterhouse NJ (2006). "Role of Bid-induced mitochondrial outer membrane permeabilization granzyme B-induced apoptosis". Immunol. Cell Biol. 84 (1): 72–8. doi:10.1111/j.1440-1711.2005.01416.x. PMID 16405654.
- ^ Choy JC (2010). "Granzymes and perforin in solid organ transplant rejection". 17 (4): 567–76. doi:10.1038/cdd.2009.161. PMID 19876069.
{{cite journal}}: Cite journal requires|journal=(help) - ^ a b Waterhouse NJ (2007). "H is for helper: granzyme H helps granzyme B kill adenovirus-infected cells". 28 (9): 373–5. doi:10.1016/j.it.2007.08.001. PMID 17766182.
{{cite journal}}: Cite journal requires|journal=(help) - ^ a b c Hiebert PR (2012). "Granzyme B in injury, inflammation, and repair". Trends Mol Med. 18 (12): 732–41. doi:10.1016/j.molmed.2012.09.009. PMID 23099058.
- ^ Kaiserman D (2010). "Control of granzymes by serpins". 17 (4): 586–95. doi:10.1038/cdd.2009.169. PMID 19893573.
{{cite journal}}: Cite journal requires|journal=(help) - ^ Darrah E (2010). "Granzyme B cleavage of autoantigens in autoimmunity". 17 (4): 624–32. doi:10.1038/cdd.2009.197. PMC 3136751. PMID 20075942.
{{cite journal}}: Cite journal requires|journal=(help) - ^ Saito Y (2011). "Granzyme B as a noverl factor involed in cardiovascular diseases". J Cardiol. 57 (2): 141–7. doi:10.1016/j.jjcc.2010.10.001. PMID 21168312.
External links
- Granzyme+B at the U.S. National Library of Medicine Medical Subject Headings (MeSH)