Neutrophil Cathepsin G Promotes Detachment-induced Cardiomyocyte Apoptosis via a Protease-activated Receptor-independent Mechanism

Abstract

Cathepsin G is a neutrophil-derived serine protease that contributes to tissue damage at sites of inflammation. The actions of cathepsin G are reported to be mediated by protease-activated receptor (PAR)-4 (a thrombin receptor) in human platelets. This study provides the first evidence that cathepsin G promotes inositol 1,4,5-trisphosphate accumulation, activates ERK, p38 MAPK, and AKT, and decreases contractile function in cardiomyocytes. Because some cathepsin G responses mimic cardiomyocyte activation by thrombin, a role for PARs was considered. Cathepsin G markedly activates phospholipase C and p38 MAPK in cardiomyocytes from PAR-1–/– mice, but it fails to activate phospholipase C, ERK, p38 MAPK, or AKT in PAR-1- or PAR-4-expressing PAR-1–/– fibroblasts (which display robust responses to thrombin). These results argue that PAR-1 does not mediate the actions of cathepsin G in cardiomyocytes, and neither PAR-1 nor PAR-4 mediates the actions of cathepsin G in fibroblasts. Of note, prolonged incubation of cardiomyocytes with cathepsin G results in the activation of caspase-3, cleavage of FAK and AKT, sarcomeric disassembly, cell rounding, cell detachment from underlying matrix, and morphologic features of apoptosis. Inhibition of Src family kinases or caspases (with PP1 or benzyloxycarbonyl-VAD-fluoromethyl ketone, respectively) delays FAK and AKT cleavage and cardiomyocyte detachment from substrate. Collectively, these studies describe novel cardiac actions of cathepsin G that do not require PARs and are predicted to assume functional importance at sites of interstitial inflammation in the heart. Cathepsin G is a neutrophil-derived serine protease that contributes to tissue damage at sites of inflammation. The actions of cathepsin G are reported to be mediated by protease-activated receptor (PAR)-4 (a thrombin receptor) in human platelets. This study provides the first evidence that cathepsin G promotes inositol 1,4,5-trisphosphate accumulation, activates ERK, p38 MAPK, and AKT, and decreases contractile function in cardiomyocytes. Because some cathepsin G responses mimic cardiomyocyte activation by thrombin, a role for PARs was considered. Cathepsin G markedly activates phospholipase C and p38 MAPK in cardiomyocytes from PAR-1–/– mice, but it fails to activate phospholipase C, ERK, p38 MAPK, or AKT in PAR-1- or PAR-4-expressing PAR-1–/– fibroblasts (which display robust responses to thrombin). These results argue that PAR-1 does not mediate the actions of cathepsin G in cardiomyocytes, and neither PAR-1 nor PAR-4 mediates the actions of cathepsin G in fibroblasts. Of note, prolonged incubation of cardiomyocytes with cathepsin G results in the activation of caspase-3, cleavage of FAK and AKT, sarcomeric disassembly, cell rounding, cell detachment from underlying matrix, and morphologic features of apoptosis. Inhibition of Src family kinases or caspases (with PP1 or benzyloxycarbonyl-VAD-fluoromethyl ketone, respectively) delays FAK and AKT cleavage and cardiomyocyte detachment from substrate. Collectively, these studies describe novel cardiac actions of cathepsin G that do not require PARs and are predicted to assume functional importance at sites of interstitial inflammation in the heart. Cathepsin G is a major serine protease released by activated neutrophils at sites of vascular injury and inflammation (1Molino M. Blanchard N. Belmonte E. Tarver A.P. Abrams C. Hoxie J.A. Cerletti C. Brass L.F. J. Biol. Chem. 1995; 270: 11168-11175Google Scholar, 2Parry M.A. Myles T. Tschopp J. Stone S.R. Biochem. J. 1996; 320: 335-341Google Scholar). Cathepsin G is a strong agonist for platelets, causing a rise in intracellular calcium, aggregation, and degranulation. Cathepsin G induces functional and morphological changes in endothelial cells that lead to increased permeability and growth factor release (1Molino M. Blanchard N. Belmonte E. Tarver A.P. Abrams C. Hoxie J.A. Cerletti C. Brass L.F. J. Biol. Chem. 1995; 270: 11168-11175Google Scholar, 3Weksler B.B. Jaffe E.A. Brower M.S. Cole O.F. Blood. 1989; 74: 1627-1634Google Scholar, 4Selak M.A. Biochem. J. 1994; 297: 269-275Google Scholar, 5Si-Tahar M. Renesto P. Falet H. Rendu F. Chignard M. Biochem. J. 1996; 313: 401-408Google Scholar). Cathepsin G also induces tissue injury and contributes to the pathogenesis of certain chronic pulmonary diseases, such as emphysema and cystic fibrosis (6Bird P.I. Immunol. Cell Biol. 1999; 77: 47-57Google Scholar). These diverse cellular actions of cathepsin G have been attributed to the cleavage and function modulation of a range of protein substrates, including clotting factors (factor V and factor VII), neutrophil chemoattractants (tumor necrosis factor α, interleukin-1, and interleukin-8), and matrix components (including collagen, fibronectin, and elastin). Recent studies have focused on cathepsin G-dependent cleavage of seven transmembrane spanning domain G protein-coupled protease-activated receptors (PARs) 1The abbreviations used are: PARs, protease-activated receptors; IP, inositol phosphate; ERK, extracellular signal-regulated kinase; MAPK, mitogen-activated protein kinase; Z, benzyloxycarbonyl; fmk, fluoromethyl ketone; PTX, pertussis toxin; DMEM, Dulbecco's modified Eagle's medium; MMPs, matrix-degrading metalloproteinases; FAK, focal adhesion kinase. as an additional potentially important mechanism whereby cathepsin G modulates coagulation and tissue remodeling at sites of injury and inflammation. PAR-1, the prototypical receptor for thrombin, is activated as a result of thrombin-dependent cleavage of its extracellular N terminus to expose a new N-terminal sequence (SFLLRN) that binds intramolecularly and serves as a tethered ligand (7Coughlin S.R. Proc. Natl. Acad. Sci. U. S. A. 1999; 96: 11023-11027Google Scholar). Since the initial cloning of PAR-1, three additional structurally homologous PARs have been identified; PAR-3 and PAR-4 are activated by thrombin, whereas PAR-2 is activated by trypsin, membrane-type serine protease-1, and mast cell tryptase (but not thrombin) (8Dery O. Corvera C.U. Steinhoff M. Bunnett N.W. Am. J. Physiol. 1998; 274: C1429-C1452Google Scholar, 9Takeuchi T. Harris J.L. Huang W. Yan K.W. Coughlin S.R. Craik C.S. J. Biol. Chem. 2000; 275: 26333-26342Google Scholar). PARs are endowed with two unique regulatory features as a result of their distinctive proteolytic activation mechanism. PAR-1, PAR-3, and PAR-4 need not be entirely selective for thrombin but are predicted to be susceptible to activation by any serine protease capable of cleaving the N terminus at the site that exposes the tethered ligand sequence. Additionally, PAR cleavage at sites on the N terminus more proximal to the transmembrane domain is predicted to amputate the tethered ligand sequence and render the PAR unresponsive to subsequent proteolytic activation. Cathepsin G is reported to modulate PAR function via both mechanisms. At concentrations achieved in the vicinity of activated neutrophils, cathepsin G mimics the action of thrombin to mobilize intracellular calcium in Xenopus oocytes and fibroblast cell lines that stably overexpress human PAR-1 or human PAR-4 (but not in untransfected cells or cells that overexpress PAR-2 or PAR-3). Mutagenesis studies suggest that in each case the mechanism entails cleavage of the N terminus (at the Arg41–Ser42 bond in PAR-1 and the Arg47–Gly48 bond in PAR-4) to expose the tethered ligand (1Molino M. Blanchard N. Belmonte E. Tarver A.P. Abrams C. Hoxie J.A. Cerletti C. Brass L.F. J. Biol. Chem. 1995; 270: 11168-11175Google Scholar, 10Sambrano G.R. Huang W. Faruqi T. Mahrus S. Craik C. Coughlin S.R. J. Biol. Chem. 2000; 275: 6819-6823Google Scholar). These results suggest that cathepsin G should display generalized agonist actions in cells that express either PAR-1 or PAR-4. However, for unclear reasons, agonist actions of cathepsin G are consistently identified in human platelets but not other thrombin-responsive cell types, such as human umbilical vein endothelial cells and human lung fibroblasts (1Molino M. Blanchard N. Belmonte E. Tarver A.P. Abrams C. Hoxie J.A. Cerletti C. Brass L.F. J. Biol. Chem. 1995; 270: 11168-11175Google Scholar, 3Weksler B.B. Jaffe E.A. Brower M.S. Cole O.F. Blood. 1989; 74: 1627-1634Google Scholar, 4Selak M.A. Biochem. J. 1994; 297: 269-275Google Scholar, 11LeRoy E.C. Ager A. Gordon J.L. J. Clin. Invest. 1984; 84: 1003-1010Google Scholar, 12Molino M. Woolkalis M. Reavey-Cantwell J. Pratico D. Andrade-Gordon P. Barnathan E.S. Brass L.F. J. Biol. Chem. 1997; 272: 11133-11141Google Scholar). Rather, in cells that express PAR-1 but do not display stimulatory responses to cathepsin G, the predominant effect of cathepsin G is to non-productively cleave PAR-1 at a site close to the first transmembrane domain (Phe55–Trp56). This amputates the tethered ligand domain and renders PAR-1 unresponsive to subsequent stimulation by thrombin (although cathepsin G-cleaved PAR-1 is otherwise structurally intact and fully responsive to SFLLRN) (1Molino M. Blanchard N. Belmonte E. Tarver A.P. Abrams C. Hoxie J.A. Cerletti C. Brass L.F. J. Biol. Chem. 1995; 270: 11168-11175Google Scholar). Recent studies (13Cumashi A. Ansuini H. Celli N. A. Brass L.F. M. that human and PAR-3 also be by cathepsin G (although via and that certain cathepsin G actions on PARs be The of PARs have been in platelets the actions of thrombin are for and and the thrombin promotes changes in endothelial cell lead to and induces of vascular However, studies cardiomyocytes as an additional for thrombin and from PAR-1, and PAR-4 for PAR-3 is not T. E. 1996; Scholar, J. Biol. Chem. Scholar, M. A. M. 1996; Scholar, E. A. S. S. M. S. J. Biol. Chem. 2000; 275: Scholar, A. H. E. A. Andrade-Gordon P. 2000; Scholar, A. J. H. Andrade-Gordon P. J. Biol. Chem. Scholar). PAR-1 and PAR-2 in and intracellular both receptors to the activation of ERK, stimulation of p38 MAPK, and cardiomyocyte A. H. E. A. Andrade-Gordon P. 2000; Scholar). Recent studies A. J. H. Andrade-Gordon P. J. Biol. Chem. that PAR-4 also activates p38 MAPK in PAR-4 activates ERK, and induces but more The predominant of cardiomyocyte PARs cardiomyocyte PAR-1 be activated by thrombin in the of the endothelial is and cardiomyocytes with are not by the other for PAR activation be considered. This study cathepsin G by neutrophils at sites of injury inflammation the of a a agonist action in cardiomyocytes and cathepsin G responses be attributed to activation of a from the thrombin pertussis Cathepsin G was from for with cathepsin G from and other and from and at the of as by and by from for from the of or PAR-1–/– or by a a to for cardiac T. E. 1996; Scholar). the decreases fibroblast to of on of to the of any fibroblasts T. E. 1996; Scholar). at a of cells and in with of ERK, p38 MAPK, or AKT cells in for Cell lung from Andrade-Gordon P. 1996; Scholar, P. D. Proc. Natl. Acad. Sci. U. S. A. 1999; 96: functional PAR-1, and with human PAR-1 or PAR-4 in a modified a in of and by calcium in and for of MAPK or AKT for or with with for and with for the at and by on to T. E. 1996; Scholar). was used to of and ERK, p38 MAPK, and AKT and to the of and FAK cleavage to as in cells three with and at for at The was in for and at was to with by and by each in each the results are from a for a of and Cell calcium and was in to T. E. 1996; Scholar). on with by incubation in of the of and of in for at with and for at at to for of the with with at a of and by stimulation at the changes in cell calcium to actions of as a the of a three T. E. 1996; Scholar). was (at a of with a that the cells with and at calcium is reported as the to the in any to these as in by and T. E. 1996; to the to for cell The cell was to a and a to the cardiomyocyte was a The of a of renders of cell in cell cell is The from the was to to of The at a of was and and on that in at in the of with or cathepsin for with a on a with or and a The was by or of and by and Cathepsin G and ERK, p38 MAPK, and AKT in by Cathepsin G and PAR that cathepsin G markedly in cardiomyocytes. are at concentrations of cathepsin G, of reported to be at sites of inflammation. The of in to PAR-1 SFLLRN) cathepsin G are with PAR-1 activation by stimulatory concentrations of thrombin or the PAR-1 agonist results in of by a more of A. E. 2000; Scholar). cathepsin G promotes the of and as or the in cells with thrombin or the cathepsin rise in is in Because identified PAR-4 as an additional cellular receptor for thrombin in cardiomyocytes A. J. H. Andrade-Gordon P. J. Biol. Chem. also responses to cathepsin G and (a of the PAR-4 tethered ligand sequence that is for PAR-4 and at concentrations the tethered ligand sequence Huang W. Coughlin S.R. J. Biol. Chem. 2000; 275: Scholar). that induces a rise in but the of is with the rise in by thrombin (a that activates in actions be attributed to robust PAR-4 in a fibroblast cardiac fibroblasts display in in to thrombin and but cardiac fibroblasts do not to A. J. J. Scholar). Of note, stimulation with results in the of with a in This is from the effect of cathepsin G, promotes the of The actions of cathepsin G and thrombin are their to the of studies that the effect of thrombin to activate phospholipase C in cardiomyocyte is by with A. E. 2000; Scholar). in to cathepsin G is not Collectively, these responses to cathepsin G PAR in cardiomyocytes, that PARs are of the cardiac actions of cathepsin of in to PAR and cathepsin in a new The studies cathepsin G activates ERK, p38 MAPK, and AKT, identified as of PARs in cardiomyocytes. that cathepsin G promotes a and in the is at and The of cathepsin G-dependent activation of is with the robust by cathepsin G markedly activates p38 MAPK and AKT to or the to thrombin) but with of p38 MAPK and AKT is at and the first of These results suggest that cathepsin G and PARs activate certain However, in the and the of these responses suggest activation mechanisms. that cathepsin G also the of cell The PAR-1 agonist induces a in contractile function However, the of cathepsin G and on intracellular calcium are and calcium and whereas cathepsin G does not intracellular The effect of cathepsin G to contractile intracellular calcium, is with a mechanism that calcium of Cathepsin G PAR-1 or PAR-4 of the cellular to cathepsin G the of an rise in are from the to PAR to suggest that cathepsin G via a mechanism. the studies of cardiomyocytes from of and PAR-1–/– to the role of PAR-1 in the stimulatory actions of cathepsin that promotes and activates p38 MAPK in cardiomyocytes from but not that the in activation be attributed to a in components of the to PAR-1, in to receptor activation with is robust in both and PAR-1–/– to require of a PAR-1 cathepsin G promotes and p38 MAPK in cardiomyocytes from both and PAR-1–/– These results that the stimulatory actions of cathepsin G in cardiomyocytes do not require PAR-1 cell lines from PAR-1–/– that stably express human PAR-1 or PAR-4 also used to a PAR for cathepsin G that thrombin and PAR agonist activate with the predicted in agonist and for is by or thrombin in cells that overexpress PAR-1 and by or thrombin in cells that overexpress PAR-4 (a receptor by thrombin each receptor stimulation with thrombin or with results in the activation of ERK, p38 MAPK, and AKT and cathepsin G promotes a in the of or in cells that overexpress cathepsin G does not in cells that express PAR-1 cathepsin G activates (but not p38 MAPK or in PAR-1- and PAR-4-expressing cell lines and at to activation by PARs is at Cathepsin G also induces a and activation of in cells that do not to thrombin or This that the of activation by cathepsin G be to activation of either PAR-1 or PAR-4. that overexpress PAR-1 a and to incubation with cathepsin cells that overexpress PAR-4 and from the underlying matrix incubation with cathepsin These morphological changes do not result from PAR-4 PAR-4 stimulation with either thrombin or does not morphologic the responses by cathepsin G in cells that overexpress PAR-4 the of cell detachment from the of cathepsin in cell adhesion and not proteolytic activation of PAR-4 by cathepsin Collectively, these results that the agonist actions of cathepsin G be attributed to the activation of either PAR-1 or PAR-4. Cathepsin G PAR-1 but PAR-2 or PAR-4 Cathepsin G cleavage that with cathepsin G for subsequent by thrombin in cells that overexpress responses to that the receptor otherwise structurally PAR-1 is susceptible to cathepsin G-dependent with cathepsin G does not subsequent by either thrombin or in cells that overexpress human PAR-4 These results evidence that PAR-4 is not a for cathepsin G also that cathepsin G PAR-1 in with cathepsin G renders cardiomyocyte to subsequent stimulation by thrombin but not by These results are the of cathepsin G identified in the of the human PAR-1 sequence. Because the cathepsin G site in human PAR-1 is not in the PAR-1 be additional sites for cathepsin G G from and G is reported to endothelial cell to increased permeability and the of a potentially C. Biol. 1995; Scholar). These of cathepsin G are from by PAR-1 cathepsin G does not activate PAR-1 in endothelial Cathepsin G induces changes in the of cardiomyocytes. of an of a cardiomyocyte and at to cathepsin The a and of cardiomyocytes Cathepsin G induces a of and such that cells and the cells and from underlying and of protein cell detachment at with to cellular in with cathepsin G for Of note, the cathepsin changes in cardiomyocyte the first are the cathepsin is and with not The of cathepsin G to release cardiomyocytes from to extracellular matrix lead to a of that results from or Cell Biol. Scholar). additional studies to cardiomyocytes with cathepsin G display the features of apoptosis. that of cathepsin G cardiomyocytes to and from the with sarcomeric protein that of the sarcomeric of cardiomyocyte also is by and of of cells cathepsin cells for at of cathepsin G of the cell with with However, the cells as with the cells and cells with to that a of and are not calcium Collectively, these results an effect of cathepsin G to an of cell Cathepsin G by Src or an important role in the of the including in cells cathepsin G promotes with an that the (which is as a result of proteolytic cleavage of the that the is not but it is to cathepsin the cleavage is at and for cathepsin G by the cleavage of and adhesion is a that is a major of focal adhesion the that the intracellular to the extracellular FAK mediated by with extracellular matrix cleavage of FAK is in endothelial cells H. J. 1998; Scholar). that incubation with cathepsin G to a in the of a of more FAK to the FAK via these H. J. 1998; Scholar). AKT is for M.A. N. T. J. Biol. Chem. Scholar). cathepsin G induces AKT but more prolonged incubation with cathepsin G to a in the of AKT studies that cleavage a domain and an domain of AKT M.A. N. T. J. Biol. Chem. Scholar, S. N. T. J. Physiol. 2000; Scholar). However, not in cardiomyocytes to cathepsin results and to the in cleavage of AKT by other that at that are or at that are to be M.A. N. T. J. Biol. Chem. Scholar). the cleavage of AKT and FAK does not result from the generalized of cellular as of and p38 MAPK these and not is evidence that activation is by Src family kinases F. N. F. P. J. Scholar, F. P. Scholar). Src kinases to the cardiac actions of cathepsin G, studies with PP1 (a Src family that PP1 the cathepsin G-dependent of PP1 also the effect of cathepsin G to activate p38 MAPK, ERK, and (although in to cathepsin G in that PP1 markedly the more chronic of cathepsin G to activate and cleave FAK cleavage is and (but not by The effect of PP1 to the activation of and cleavage of AKT to a that these are with of AKT and FAK in cardiomyocytes to cathepsin G in the of (a These results Src kinases and in the for AKT and FAK cleavage cathepsin G that the of PP1 and to the of delays the of cell but neither is to the morphologic changes by cathepsin This study provides the first evidence that neutrophil cathepsin G as a agonist for cardiomyocytes. Cathepsin G a of responses that in mimic cardiomyocyte activation by both cathepsin G and thrombin activate and p38 MAPK AKT, and contractile The stimulatory of thrombin have been attributed to proteolytic activation of studies A. J. H. Andrade-Gordon P. J. Biol. Chem. PAR-4 as an additional for the action of thrombin in cardiomyocytes. However, are the responses by stimulatory concentrations of PAR or cathepsin G that that a PAR mediates the action of cathepsin G in cardiomyocytes. thrombin and the PAR-1 agonist in and are by a more in the of is of the G protein-coupled to the activation of phospholipase C. cathepsin G promotes the of and with and of the of of does not to any G protein-coupled receptor reported The of PAR and cathepsin G on intracellular calcium also PAR-1 activation with thrombin or results in a rise in intracellular intracellular calcium does not with cathepsin G (although an effect of prolonged cathepsin G stimulation to intracellular calcium to cathepsin changes in cell are and not be by these These in PAR-1 agonist cathepsin G actions the first that the cardiac actions of cathepsin G not be to proteolytic cleavage of a The of cardiomyocytes to PAR is sarcomeric and cathepsin G activation of caspases to cleavage of and and cardiomyocyte detachment from underlying evidence that thrombin and cathepsin G via used to a role for PARs in the actions of cathepsin with studies that PAR-1 function as a for cathepsin G cleavage certain in but that PAR-1 does not mediate cathepsin G responses in the studies reported that PAR-1 is not for cathepsin G responses in cardiomyocytes. C and p38 MAPK activation by cathepsin G is in and PAR-1–/– cardiomyocytes. study PAR-4 in the cellular actions of cathepsin G in human platelets that PAR-4 as a cathepsin G receptor in human PAR-4-expressing Xenopus oocytes and lung fibroblasts from PAR-1–/– G.R. Huang W. Faruqi T. Mahrus S. Craik C. Coughlin S.R. J. Biol. Chem. 2000; 275: 6819-6823Google Scholar). The evidence to the that human PAR-4 activation by cathepsin G is cathepsin G calcium release from oocytes that express human PAR-4 but not from oocytes that express a PAR-4 to at of the agonist that is to thrombin cleavage but responsive to However, the evidence PAR-4 cleavage as the mechanism cathepsin G actions in fibroblasts is more The are to the that cathepsin G intracellular calcium in but not lung fibroblasts G.R. Huang W. Faruqi T. Mahrus S. Craik C. Coughlin S.R. J. Biol. Chem. 2000; 275: 6819-6823Google Scholar). evidence that cathepsin G PAR-4 been This is as a that the actions of cathepsin G to an cleavage of PAR-4 does not results (13Cumashi A. Ansuini H. Celli N. A. Brass L.F. M. in platelets, cathepsin G does not that cathepsin G does not activate reported also are more with a mechanism for cathepsin G studies that of human PAR-4 to thrombin and but not to cathepsin cathepsin G does not mimic the actions of thrombin to activate proximal accumulation, ERK, p38 MAPK, and in PAR-1–/– fibroblasts that express PAR-4. The that cathepsin cells fully responsive to the stimulatory actions of thrombin that cathepsin G also does not cleave PAR-4 at a site that amputates the tethered ligand These results that PAR-4 cleavage contributes to the actions of cathepsin The in cathepsin G and the study are not to be to in of as both studies on of PAR-1–/– lung fibroblasts that stably express human PAR-4. Rather, it is to that study (which phospholipase C a proximal in the provides a more of PAR-4 activation. the cathepsin G-dependent rise in intracellular calcium identified in the study PAR-4 PAR-1–/– lung fibroblasts the of cathepsin changes in cell to such a calcium be in cells that overexpress display the morphologic changes incubation with cathepsin the that cathepsin G induces morphologic changes in cells that express but effect in cells that express PAR-1, that PAR-4 activation to changes in cell receptor adhesion that render cells susceptible to the actions of cathepsin G that these cell a to the of the actions of cathepsin The cathepsin changes in cardiomyocyte in study are of the changes in endothelial cell an initial effect of cathepsin G to and expose the underlying extracellular matrix the of the and a potentially is by cleavage of extracellular matrix components and C. Biol. 1995; Scholar). The underlying the cellular actions of cathepsin G are is some evidence that cathepsin G promotes tissue remodeling by components of the However, cathepsin G also by cleaving and matrix-degrading are in the extracellular as Cathepsin cleavage of been as a mechanism for tissue remodeling and injury in the P. S. D. P. J. Physiol. Scholar). in a effect of cathepsin G to release from cardiomyocyte studies to the for activation and the role of in the cardiac actions of cathepsin G are and S. F. in This study provides novel evidence that neutrophil-derived cathepsin G cardiac injury by and the activation of The for cleavage in cardiomyocytes to cathepsin G components of the adhesion that as as for cell a mechanism that contributes to cathepsin cleavage of FAK contributes to the of the both by from the extracellular matrix and by of the focal adhesion H. J. 1998; Scholar). The cleavage of FAK results in a in of FAK and the of FAK that structurally the (a FAK that FAK to site of decreases FAK and both the of focal and cells from the by extracellular matrix cleavage of AKT is to to by of AKT a such that are S. N. T. J. Physiol. 2000; Scholar, A. S. J. Cell Biol. 1999; Scholar). cleavage of the Src family been identified as a mechanism to its and also be predicted to mediate the cardiac actions of cathepsin G F. N. F. P. J. Scholar). a study C. M. P. J. Proc. Natl. Acad. Sci. U. S. A. cleavage of certain (including and as a mechanism that and the functional of cardiomyocytes. and cleavage is in cathepsin cardiomyocytes and not that also to the pathogenesis of cathepsin G-dependent actions in the heart. The of cardiomyocytes as a cathepsin cell that a protease other thrombin and to changes in cardiomyocyte and function in a potentially protease actions have been to cleavage of PARs, these studies suggest a novel mechanism for that modulate cardiomyocyte The of cathepsin G on be important in of interstitial such as the to a neutrophil to important changes in cardiomyocyte contractile and apoptosis. neutrophils are to to tissue remodeling injury in via the release of and proteolytic However, the importance of been to These in the of evidence that (a serine protease of neutrophil cathepsin G and necrosis and in in the T. 1995; 274: suggest that neutrophil-derived such as cathepsin G be a important of cardiac for and also