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P2X7 receptor activation regulates rapid unconventional export of transglutaminase-2.

Adamczyk M, Griffiths R, Dewitt S, Knäuper V, Aeschlimann D - J. Cell. Sci. (2015)

Bottom Line: Neither Ca(2+) signaling alone nor membrane depolarization triggered TG2 secretion, which occurred only upon receptor membrane pore formation and without pannexin channel involvement.A gain-of-function mutation in P2X7R associated with autoimmune disease caused enhanced TG2 externalization from cells, and this correlated with increased pore activity.These results provide a mechanistic explanation for a link between active TG2 secretion and inflammatory responses, and aberrant enhanced TG2 activity in certain autoimmune conditions.

View Article: PubMed Central - PubMed

Affiliation: Matrix Biology & Tissue Repair Research Unit and Arthritis Research UK Biomechanics and Bioengineering Center of Excellence, College of Biomedical and Life Sciences, Cardiff University, Cardiff CF14 4XY, UK AdamczykM@Cardiff.ac.uk AeschlimannDP@Cardiff.ac.uk.

No MeSH data available.


Related in: MedlinePlus

Mechanism controlling TG2 export. Schematic showing different events occurring upon P2X7R activation by ATP. (A) Ion channel activity triggers intracellular signaling that results in actin reorganization and microvesicle shedding. However, these microvesicles do not contain TG2. (B) Coupling between P2X7R and pannexin-1 triggers hemichannel pore opening. TG2 secretion is unaffected by blocking pannexin-1 channels. (C) P2X7R itself can form a membrane pore through conformational changes and, possibly, receptor oligomerization in a process that involves the extended intracellular C-terminal sequence. TG2 secretion is associated with this membrane pore activity but independent of ion channel function, and occurs in conjunction with thioredoxin-1 (Trx) externalization. As thioredoxin can reactivate TG2 functionally blocked in an oxidized state, this might ensure that externalized TG2 has transamidation activity. Flot2, flotillin-2.
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JCS175968F8: Mechanism controlling TG2 export. Schematic showing different events occurring upon P2X7R activation by ATP. (A) Ion channel activity triggers intracellular signaling that results in actin reorganization and microvesicle shedding. However, these microvesicles do not contain TG2. (B) Coupling between P2X7R and pannexin-1 triggers hemichannel pore opening. TG2 secretion is unaffected by blocking pannexin-1 channels. (C) P2X7R itself can form a membrane pore through conformational changes and, possibly, receptor oligomerization in a process that involves the extended intracellular C-terminal sequence. TG2 secretion is associated with this membrane pore activity but independent of ion channel function, and occurs in conjunction with thioredoxin-1 (Trx) externalization. As thioredoxin can reactivate TG2 functionally blocked in an oxidized state, this might ensure that externalized TG2 has transamidation activity. Flot2, flotillin-2.

Mentions: A mutation in mouse P2X7R renders it deficient in pore-forming activity (Sorge et al., 2012). As the affected sequence motif in the P2X7R C-terminal domain is conserved in humans, we generated cells expressing human P2X7R with the analogous mutation P451L (Fig. 7B,C). However, these cells formed membrane pores in response to BzATP as revealed by YO-PRO1 uptake (Fig. 7D). This led us to investigate the gain-of-function P2X7R variant, A348T, which confers increased risk for autoimmune disease in man (Stokes et al., 2010), to substantiate a link between pore formation and TG2 secretion. Cells expressing P2X7R A348T (Fig. 7B,C) had a substantially increased propensity to form membrane pores as evidenced by enhanced peak pore activity (Fig. 7D) and by pore formation at very low BzATP concentrations (Fig. 7E). This enhanced pore activity was reflected in a corresponding increase in TG2 export (Fig. 7F,G). Interestingly, we also observed BzATP-induced secretion of thioredoxin-1 (Fig. 7H), an enzyme that can re-activate oxidatively inactivated TG2. This not only indicates that membrane pore activity controls the rate of TG2 export but that it leads to co-secretion of TG2 with thioredoxin-1 (Fig. 8).Fig. 8.


P2X7 receptor activation regulates rapid unconventional export of transglutaminase-2.

Adamczyk M, Griffiths R, Dewitt S, Knäuper V, Aeschlimann D - J. Cell. Sci. (2015)

Mechanism controlling TG2 export. Schematic showing different events occurring upon P2X7R activation by ATP. (A) Ion channel activity triggers intracellular signaling that results in actin reorganization and microvesicle shedding. However, these microvesicles do not contain TG2. (B) Coupling between P2X7R and pannexin-1 triggers hemichannel pore opening. TG2 secretion is unaffected by blocking pannexin-1 channels. (C) P2X7R itself can form a membrane pore through conformational changes and, possibly, receptor oligomerization in a process that involves the extended intracellular C-terminal sequence. TG2 secretion is associated with this membrane pore activity but independent of ion channel function, and occurs in conjunction with thioredoxin-1 (Trx) externalization. As thioredoxin can reactivate TG2 functionally blocked in an oxidized state, this might ensure that externalized TG2 has transamidation activity. Flot2, flotillin-2.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4696497&req=5

JCS175968F8: Mechanism controlling TG2 export. Schematic showing different events occurring upon P2X7R activation by ATP. (A) Ion channel activity triggers intracellular signaling that results in actin reorganization and microvesicle shedding. However, these microvesicles do not contain TG2. (B) Coupling between P2X7R and pannexin-1 triggers hemichannel pore opening. TG2 secretion is unaffected by blocking pannexin-1 channels. (C) P2X7R itself can form a membrane pore through conformational changes and, possibly, receptor oligomerization in a process that involves the extended intracellular C-terminal sequence. TG2 secretion is associated with this membrane pore activity but independent of ion channel function, and occurs in conjunction with thioredoxin-1 (Trx) externalization. As thioredoxin can reactivate TG2 functionally blocked in an oxidized state, this might ensure that externalized TG2 has transamidation activity. Flot2, flotillin-2.
Mentions: A mutation in mouse P2X7R renders it deficient in pore-forming activity (Sorge et al., 2012). As the affected sequence motif in the P2X7R C-terminal domain is conserved in humans, we generated cells expressing human P2X7R with the analogous mutation P451L (Fig. 7B,C). However, these cells formed membrane pores in response to BzATP as revealed by YO-PRO1 uptake (Fig. 7D). This led us to investigate the gain-of-function P2X7R variant, A348T, which confers increased risk for autoimmune disease in man (Stokes et al., 2010), to substantiate a link between pore formation and TG2 secretion. Cells expressing P2X7R A348T (Fig. 7B,C) had a substantially increased propensity to form membrane pores as evidenced by enhanced peak pore activity (Fig. 7D) and by pore formation at very low BzATP concentrations (Fig. 7E). This enhanced pore activity was reflected in a corresponding increase in TG2 export (Fig. 7F,G). Interestingly, we also observed BzATP-induced secretion of thioredoxin-1 (Fig. 7H), an enzyme that can re-activate oxidatively inactivated TG2. This not only indicates that membrane pore activity controls the rate of TG2 export but that it leads to co-secretion of TG2 with thioredoxin-1 (Fig. 8).Fig. 8.

Bottom Line: Neither Ca(2+) signaling alone nor membrane depolarization triggered TG2 secretion, which occurred only upon receptor membrane pore formation and without pannexin channel involvement.A gain-of-function mutation in P2X7R associated with autoimmune disease caused enhanced TG2 externalization from cells, and this correlated with increased pore activity.These results provide a mechanistic explanation for a link between active TG2 secretion and inflammatory responses, and aberrant enhanced TG2 activity in certain autoimmune conditions.

View Article: PubMed Central - PubMed

Affiliation: Matrix Biology & Tissue Repair Research Unit and Arthritis Research UK Biomechanics and Bioengineering Center of Excellence, College of Biomedical and Life Sciences, Cardiff University, Cardiff CF14 4XY, UK AdamczykM@Cardiff.ac.uk AeschlimannDP@Cardiff.ac.uk.

No MeSH data available.


Related in: MedlinePlus