Key points are not available for this paper at this time.
Caspases are universal effectors of apoptosis. The mitochondrial and death receptor pathways activate distinct apical caspases (caspase-9 and -8, respectively) that converge on the proteolytic activation of the downstream executioner caspase-3. Caspase-9 and -8 cleave procaspase-3 to produce a p24 processing intermediate (composed of its prodomain and large subunit), which then undergoes autoproteolytic cleavage to remove the prodomain from the active protease. Recently, several heat shock proteins have been shown to selectively inhibit the mitochondrial apoptotic pathway by disrupting the activation of caspase-9 downstream of cytochrome c release. We report here that the small heat shock protein αB-crystallin inhibits both the mitochondrial and death receptor pathways. In S-100 cytosolic extracts treated with cytochromec/dATP or caspase-8, αB-crystallin inhibits the autoproteolytic maturation of the p24 partially processed caspase-3 intermediate. In contrast, neither the closely related small heat shock protein family member Hsp27 nor Hsp70 inhibited the maturation of the p24 intermediate. We also demonstrate that αB-crystallin co-immunoprecipitates with the p24 partially processed caspase-3in vivo. Taken together, our results demonstrate that αB-crystallin is a novel negative regulator of apoptosis that acts distally in the conserved cell death machinery by inhibiting the autocatalytic maturation of caspase-3. Caspases are universal effectors of apoptosis. The mitochondrial and death receptor pathways activate distinct apical caspases (caspase-9 and -8, respectively) that converge on the proteolytic activation of the downstream executioner caspase-3. Caspase-9 and -8 cleave procaspase-3 to produce a p24 processing intermediate (composed of its prodomain and large subunit), which then undergoes autoproteolytic cleavage to remove the prodomain from the active protease. Recently, several heat shock proteins have been shown to selectively inhibit the mitochondrial apoptotic pathway by disrupting the activation of caspase-9 downstream of cytochrome c release. We report here that the small heat shock protein αB-crystallin inhibits both the mitochondrial and death receptor pathways. In S-100 cytosolic extracts treated with cytochromec/dATP or caspase-8, αB-crystallin inhibits the autoproteolytic maturation of the p24 partially processed caspase-3 intermediate. In contrast, neither the closely related small heat shock protein family member Hsp27 nor Hsp70 inhibited the maturation of the p24 intermediate. We also demonstrate that αB-crystallin co-immunoprecipitates with the p24 partially processed caspase-3in vivo. Taken together, our results demonstrate that αB-crystallin is a novel negative regulator of apoptosis that acts distally in the conserved cell death machinery by inhibiting the autocatalytic maturation of caspase-3. tumor necrosis factor heat shock protein Dulbecco's modified Eagle's medium fetal calf serum cycloheximide polymerase chain reaction, mAb, monoclonal antibody green fluorescent protein polyacrylamide gel electrophoresis immunoprecipitate Fas-associated death domain protein The caspase family of cysteine proteases are critical effectors of apoptosis that selectively cleave key proteins at aspartate residues, thereby altering their function to promote cell death (1Cryns V.L. Yuan J. Genes Dev. 1998; 12: 1551-1570Crossref PubMed Scopus (1161) Google Scholar, 2Thornberry N.A. Lazebnik Y. Science. 1998; 281: 1312-1316Crossref PubMed Scopus (6159) Google Scholar). Caspases are synthesized as proenzymes that are activated by trans- or auto-proteolytic cleavage at aspartate residues. They are arranged in a proteolytic cascade with some acting as initiators (-8, -9, and -10) and others acting as downstream executioners (-3, -6, and-7). The apical caspases are activated by two principal mechanisms, the mitochondrial and death receptor pathways, that converge on the proteolytic activation of caspase-3. In the former pathway, mitochondria respond to a variety of stimuli including genotoxic stress by releasing cytochrome c into the cytosol (3Liu X. Kim C.N. Yang J. Jemmerson R. Wang X. Cell. 1996; 86: 147-157Abstract Full Text Full Text PDF PubMed Scopus (4463) Google Scholar). Cytochromec then binds to Apaf-1, which oligomerizes in the presence of ATP and recruits/activates procaspase-9; this multimeric complex is often referred to as the apoptosome (4Zou H. Henzel W. Liu X. Lutschg A. Wang X. Cell. 1997; 90: 405-413Abstract Full Text Full Text PDF PubMed Scopus (2743) Google Scholar, 5Srinivasula S.M. Ahmad M. Fernandes-Alnemri T. Alnemri E.S. Mol. Cell. 1998; 1: 949-957Abstract Full Text Full Text PDF PubMed Scopus (969) Google Scholar). In the death receptor pathway, members of the tumor necrosis factor (TNF)1-α family bind to their receptors, thereby recruiting and activating procaspase-8 via a series of protein-protein interactions mediated by FADD (6Muzio M. Chinnaiyan A.M. Kischkel F.C. O'Rourke K. Shevchenko A. Ni J. Scaffidi C. Bretz J.D. Zhang M. Gentz R. Mann M. Krammer P.H. Peter M.E. Dixit V.M. Cell. 1996; 85: 817-827Abstract Full Text Full Text PDF PubMed Scopus (2741) Google Scholar, 7Boldin M.P. Goncharov T.M. Goltsev Y.V. Wallach D. Cell. 1996; 85: 803-815Abstract Full Text Full Text PDF PubMed Scopus (2111) Google Scholar). Active caspase-9 (the mitochondrial pathway) or caspase-8 (the death receptor pathway) then initiate the proteolytic activation of procaspase-3 by a multi-step mechanism. In the first step, caspase-9 or -8 cleaves procaspase-3 at an aspartate residue between its large and small subunits to generate a p24 intermediate (the prodomain and the large subunit) and the p12 small subunit (8Fernandes-Alnemri T. Armstrong R.C. Krebs J. Srinivasula S.M. Wang L. Bullrich F. Fritz L.C. Trapani J.A. Tomaselli K.J. Litwack G. Alnemri E.S. Proc. Natl. Acad. Sci. U. S. A. 1996; 93: 7464-7469Crossref PubMed Scopus (693) Google Scholar, 9Martin S.J. Amarante-Mendes G.P. Shi L. Chuang T.-H. Casiano C.A. O'Brien G.A. Fitzgerald P. Tan E.M. Bokoch G.M. Greenberg A.H. Green D.M. EMBO J. 1996; 15: 2407-2416Crossref PubMed Scopus (273) Google Scholar, 10Li P. Nijhawan D. Budihardjo I. Srinivasula S.M. Ahmad M. Alnemri E.S. Wang X. Cell. 1997; 91: 479-489Abstract Full Text Full Text PDF PubMed Scopus (6239) Google Scholar, 11Han Z. Hendrickson E.A. Bremner T.A. Wyche J.H. J. Biol. Chem. 1997; 272: 13432-13436Abstract Full Text Full Text PDF PubMed Scopus (219) Google Scholar, 12Deveraux Q.L. Roy N. Stennicke H.R. Van Arsdale T. Zhou Q. Srinivasula S.M. Alnemri E.S. Salvesen G.S. Reed J.C. EMBO J. 1998; 17: 2215-2223Crossref PubMed Scopus (1242) Google Scholar). Next, the prodomain is removed from the p24 intermediate by an autoproteolytic event to generate the p20 and p17 forms of the large subunit (8Fernandes-Alnemri T. Armstrong R.C. Krebs J. Srinivasula S.M. Wang L. Bullrich F. Fritz L.C. Trapani J.A. Tomaselli K.J. Litwack G. Alnemri E.S. Proc. Natl. Acad. Sci. U. S. A. 1996; 93: 7464-7469Crossref PubMed Scopus (693) Google Scholar, 9Martin S.J. Amarante-Mendes G.P. Shi L. Chuang T.-H. Casiano C.A. O'Brien G.A. Fitzgerald P. Tan E.M. Bokoch G.M. Greenberg A.H. Green D.M. EMBO J. 1996; 15: 2407-2416Crossref PubMed Scopus (273) Google Scholar, 10Li P. Nijhawan D. Budihardjo I. Srinivasula S.M. Ahmad M. Alnemri E.S. Wang X. Cell. 1997; 91: 479-489Abstract Full Text Full Text PDF PubMed Scopus (6239) Google Scholar, 11Han Z. Hendrickson E.A. Bremner T.A. Wyche J.H. J. Biol. Chem. 1997; 272: 13432-13436Abstract Full Text Full Text PDF PubMed Scopus (219) Google Scholar, 12Deveraux Q.L. Roy N. Stennicke H.R. Van Arsdale T. Zhou Q. Srinivasula S.M. Alnemri E.S. Salvesen G.S. Reed J.C. EMBO J. 1998; 17: 2215-2223Crossref PubMed Scopus (1242) Google Scholar). Active caspase-3 (two p17/p12 heterodimers) then induces the cell to undergo apoptosis by proteolyzing key cellular targets. Many of the stress stimuli that are capable of triggering apoptosis, such as oxidative stress and heat shock, induce the synthesis of diverse heat shock proteins (HSPs) that confer a protective effect against a wide range of cellular stresses. Recent evidence indicates that many HSPs are anti-apoptotic and directly inhibit caspase activation. For instance, Hsp70 and Hsp90 bind to Apaf-1 and prevent the recruitment of procaspase-9 to the apoptosome, thereby inhibiting caspase-9 activation (13Beere H.M. Wolf B.B. Cain K. Mosser D.D. Mahboubi A. Kuwana T. Tailor P. Morimoto R.I. Cohen G.M. Green D.R. Nat. Cell Biol. 2000; 2: 469-475Crossref PubMed Scopus (1289) Google Scholar, 14Pandey P. Saleh A. Nakazawa A. Kumar S. Srinivasula S.M. Kumar V. Weichselbaum R. Nalin C. Alnemri E.S. Kufe D. Kharbanda S. EMBO J. 2000; 19: 4310-4322Crossref PubMed Scopus (489) Google Scholar, 15Saleh A. Srinivasula S.M. Balkir L. Robbins P.D. Alnemri E.S. Nat. Cell Biol. 2000; 2: 476-483Crossref PubMed Scopus (737) Google Scholar). In contrast, Hsp27, a member of the small HSP family, has been shown to bind/sequester cytosolic cytochromec from the apoptosome and prevent procaspase-9 activation (16Bruey J.M. Ducasse C. Bonniaud P. Ravagnan L. Susin S.A. Diaz-Latoud C. Gurbuxani S. Arrigo A.P. Kroemer G. Solary E. Garrido C. Nat. Cell Biol. 2000; 2: 645-652Crossref PubMed Scopus (834) Google Scholar). However, others have demonstrated that Hsp27 antagonizes apoptosis downstream of caspase-9 activation by binding to procaspase-3 and blocking its proteolytic activation (17Pandey P. Farber R. Nakazawa A. Kumar S. Bharti A. Nalin C. Weichselbaum R. Kufe D. Kharbanda S. Oncogene. 2000; 19: 1975-1981Crossref PubMed Scopus (261) Google Scholar). These studies indicate that some HSPs, and presumably others, confer resistance to apoptosis by specifically inhibiting one or more components of the apoptotic machinery. In the present report, we examined the anti-apoptotic mechanisms of αB-crystallin, a small HSP family member related to Hsp27. Members of the small HSP family contain a highly conserved α-crystallin domain that is flanked by largely divergent amino- and carboxyl-terminal domains (18Clark J.I. Muchowski P.J. Curr. Opin. Struct. Biol. 2000; 10: 52-59Crossref PubMed Scopus (220) Google Scholar). They form oligomeric complexes that function as molecular chaperones to facilitate protein folding and prevent aggregation of denatured or misfolded proteins (18Clark J.I. Muchowski P.J. Curr. Opin. Struct. Biol. 2000; 10: 52-59Crossref PubMed Scopus (220) Google Scholar). αB-crystallin is constitutively expressed in many tissues, and it is particularly abundant in the lens, heart, skeletal muscle and in some cancers (18Clark J.I. Muchowski P.J. Curr. Opin. Struct. Biol. 2000; 10: 52-59Crossref PubMed Scopus (220) Google Scholar, 19Kato K. Shinohara H. Kurobe N. Inaguma Y. Shimizu K. Ohshima K. Biochim. Biophys. Acta. 1991; 1074: 201-208Crossref PubMed Scopus (188) Google Scholar). The expression of αB-crystallin is also induced by diverse cellular stresses (20Klemenz R. Frohli E. Steiger R.H. Schafer R. Aoyama A. Proc. Natl. Acad. Sci. U. S. A. 1991; 88: 3652-3656Crossref PubMed Scopus (479) Google Scholar). Moreover, αB-crystallin has been shown to protect cells against apoptosis induced by DNA-damaging agents, TNF-α, and Fas (21Mehlen P. Kretz-Remy C. Preville X. Arrigo A.P. EMBO J. 1996; 15: 2695-2706Crossref PubMed Scopus (518) Google Scholar, 22Mehlen P. Schulze-Osthoff K. Arrigo A.P. J. Biol. Chem. 1996; 271: 16510-16514Abstract Full Text Full Text PDF PubMed Scopus (582) Google Scholar). However, the molecular mechanisms of αB-crystallin's anti-apoptotic have been We report here that αB-crystallin antagonizes cytochrome and activation of caspase-3 by binding to partially processed caspase-3 and inhibiting its autoproteolytic cells in with fetal calf serum and cells in medium with The αB-crystallin from αB-crystallin with the and The Hsp27 from the and The then with and and into a modified in which the of the by J. by and cells on and with of αB-crystallin or Hsp27, or of to the For cells with of or and to then by in examined expression of αB-crystallin by with as V.L. L. H. H. Yuan J. J. Biol. Chem. 1996; 271: Full Text Full Text PDF PubMed Scopus Google Scholar). cells treated with or and cycloheximide cells by or or with as and V. Cell In Scholar). as the of cells that by with as and V. Cell In Scholar). For cells or two αB-crystallin or treated with or and cells then apoptosis as cells in and in The is as the the of by a αB-crystallin and Hsp27 the to the The αB-crystallin from the αB-crystallin with the and The Hsp27 from the Hsp27 the and The then with and or and and into the in by proteins to the proteins from and at S-100 extracts from cells as (3Liu X. Kim C.N. Yang J. Jemmerson R. Wang X. Cell. 1996; 86: 147-157Abstract Full Text Full Text PDF PubMed Scopus (4463) Google that cells by in a For procaspase-9 activation S-100 extracts in the or presence of αB-crystallin Hsp27 or Hsp70 and procaspase-9 from procaspase-9 the to the Caspases activated by the of cytochrome c at or of caspase-8 at The by and by as V.L. L. H. H. Yuan J. J. Biol. Chem. 1996; 271: Full Text Full Text PDF PubMed Scopus Google Scholar, V. Y. A. H. K. L. P. M. Yuan J. J. Biol. Chem. 1997; 272: Full Text Full Text PDF PubMed Scopus Google Scholar). The procaspase-3 and activation studies as that procaspase-9 and the by with caspase-3 or V.L. L. H. H. Yuan J. J. Biol. Chem. 1996; 271: Full Text Full Text PDF PubMed Scopus Google Scholar). cells or in at a of and on then at at The with protein and of or at then in and the proteins by with αB-crystallin or caspase-3 as V.L. L. H. H. Yuan J. J. Biol. Chem. 1996; 271: Full Text Full Text PDF PubMed Scopus Google Scholar). the mechanisms by which αB-crystallin inhibits apoptosis, we examined expression of αB-crystallin cells from stimuli that the mitochondrial pathway (the DNA-damaging or the death receptor pathway cells or which αB-crystallin with or cells treated with or and and the of cells with apoptotic demonstrated in expression of αB-crystallin inhibited apoptosis induced by or Hsp27, a small HSP family member closely related to αB-crystallin, also a of against and apoptosis. We also shown in the and αB-crystallin also against apoptosis induced by and with These demonstrate that αB-crystallin inhibits both the mitochondrial and death receptor apoptotic pathways. In two pathways converge on the proteolytic activation of that αB-crystallin apoptosis by inhibiting caspase-3 activation downstream by both pathways. We first examined the of αB-crystallin to inhibit the activation of procaspase-9 and procaspase-3 in S-100 cytosolic the range of of αB-crystallin are with in a variety of cell constitutively or in to heat and V. shown in the of of cytochrome c and to S-100 extracts induced the cleavage of procaspase-9 to its proteolytic by an at inhibited the proteolytic processing of procaspase-9 with Hsp27 and Hsp70 the is with the of Hsp27 and Hsp70 to apoptosome and prevent procaspase-9 activation (13Beere H.M. Wolf B.B. Cain K. Mosser D.D. Mahboubi A. Kuwana T. Tailor P. Morimoto R.I. Cohen G.M. Green D.R. Nat. Cell Biol. 2000; 2: 469-475Crossref PubMed Scopus (1289) Google Scholar, 15Saleh A. Srinivasula S.M. Balkir L. Robbins P.D. Alnemri E.S. Nat. Cell Biol. 2000; 2: 476-483Crossref PubMed Scopus (737) Google Scholar, J.M. Ducasse C. Bonniaud P. Ravagnan L. Susin S.A. Diaz-Latoud C. Gurbuxani S. Arrigo A.P. Kroemer G. Solary E. Garrido C. Nat. Cell Biol. 2000; 2: 645-652Crossref PubMed Scopus (834) Google Scholar). demonstrated in the of cytochrome c and to S-100 extracts also the cleavage of procaspase-3 into its p20 and p17 forms of the large subunit by the caspase-3 in studies the small p12 However, the of αB-crystallin to the of the p24 partially processed caspase-3 the large subunit) with a in the of processed particularly The p24 processing intermediate at of αB-crystallin as as of the αB-crystallin is in to the p24 partially processed we demonstrated that the caspase-3 with αB-crystallin The of the caspase-3 maturation by αB-crystallin is demonstrated by αB-crystallin's in the proteolytic processing of a downstream of caspase-3. In contrast, neither Hsp27 nor Hsp70 to the of the p24 intermediate in S-100 extracts with of both Hsp27 and Hsp70 inhibited the caspase-9 cleavage of with their of caspase-9 activation by cytochrome c (13Beere H.M. Wolf B.B. Cain K. Mosser D.D. Mahboubi A. Kuwana T. Tailor P. Morimoto R.I. Cohen G.M. Green D.R. Nat. Cell Biol. 2000; 2: 469-475Crossref PubMed Scopus (1289) Google Scholar, 15Saleh A. Srinivasula S.M. Balkir L. Robbins P.D. Alnemri E.S. Nat. Cell Biol. 2000; 2: 476-483Crossref PubMed Scopus (737) Google J.M. Ducasse C. Bonniaud P. Ravagnan L. Susin S.A. Diaz-Latoud C. Gurbuxani S. Arrigo A.P. Kroemer G. Solary E. Garrido C. Nat. Cell Biol. 2000; 2: 645-652Crossref PubMed Scopus (834) Google Scholar). the maturation of the p24 partially processed caspase-3 the autocatalytic of its prodomain (8Fernandes-Alnemri T. Armstrong R.C. Krebs J. Srinivasula S.M. Wang L. Bullrich F. Fritz L.C. Trapani J.A. Tomaselli K.J. Litwack G. Alnemri E.S. Proc. Natl. Acad. Sci. U. S. A. 1996; 93: 7464-7469Crossref PubMed Scopus (693) Google Scholar, 9Martin S.J. Amarante-Mendes G.P. Shi L. Chuang T.-H. Casiano C.A. O'Brien G.A. Fitzgerald P. Tan E.M. Bokoch G.M. Greenberg A.H. Green D.M. EMBO J. 1996; 15: 2407-2416Crossref PubMed Scopus (273) Google Scholar, 10Li P. Nijhawan D. Budihardjo I. Srinivasula S.M. Ahmad M. Alnemri E.S. Wang X. Cell. 1997; 91: 479-489Abstract Full Text Full Text PDF PubMed Scopus (6239) Google Scholar, 11Han Z. Hendrickson E.A. Bremner T.A. Wyche J.H. J. Biol. Chem. 1997; 272: 13432-13436Abstract Full Text Full Text PDF PubMed Scopus (219) Google Scholar, 12Deveraux Q.L. Roy N. Stennicke H.R. Van Arsdale T. Zhou Q. Srinivasula S.M. Alnemri E.S. Salvesen G.S. Reed J.C. EMBO J. 1998; 17: 2215-2223Crossref PubMed Scopus (1242) Google indicate that the principal by which αB-crystallin inhibits the cytochrome activation of caspase-3 is by blocking its autoproteolytic We examined αB-crystallin inhibited the activation of procaspase-3 in S-100 In this procaspase-3 is directly by caspase-8 to generate the p24 and the prodomain is removed by autoproteolytic cleavage to produce the forms of the large subunit (8Fernandes-Alnemri T. Armstrong R.C. Krebs J. Srinivasula S.M. Wang L. Bullrich F. Fritz L.C. Trapani J.A. Tomaselli K.J. Litwack G. Alnemri E.S. Proc. Natl. Acad. Sci. U. S. A. 1996; 93: 7464-7469Crossref PubMed Scopus (693) Google Scholar, 9Martin S.J. Amarante-Mendes G.P. Shi L. Chuang T.-H. Casiano C.A. O'Brien G.A. Fitzgerald P. Tan E.M. Bokoch G.M. Greenberg A.H. Green D.M. EMBO J. 1996; 15: 2407-2416Crossref PubMed Scopus (273) Google Scholar, 10Li P. Nijhawan D. Budihardjo I. Srinivasula S.M. Ahmad M. Alnemri E.S. Wang X. Cell. 1997; 91: 479-489Abstract Full Text Full Text PDF PubMed Scopus (6239) Google Scholar, 11Han Z. Hendrickson E.A. Bremner T.A. Wyche J.H. J. Biol. Chem. 1997; 272: 13432-13436Abstract Full Text Full Text PDF PubMed Scopus (219) Google Scholar, 12Deveraux Q.L. Roy N. Stennicke H.R. Van Arsdale T. Zhou Q. Srinivasula S.M. Alnemri E.S. Salvesen G.S. Reed J.C. EMBO J. 1998; 17: 2215-2223Crossref PubMed Scopus (1242) Google Scholar). demonstrated in of S-100 extracts with active caspase-8 to the cleavage of procaspase-3 to p20 and However, the of αB-crystallin to the of the p24 processing intermediate and a in the of processed In contrast, Hsp27 or Hsp70 to the of the p24 intermediate. Moreover, neither Hsp27 nor Hsp70 inhibited the cleavage of procaspase-3 by αB-crystallin inhibit activation in S-100 extracts treated with caspase-8 caspase-8 directly cleave caspase-3 activation is processing in this (8Fernandes-Alnemri T. Armstrong R.C. Krebs J. Srinivasula S.M. Wang L. Bullrich F. Fritz L.C. Trapani J.A. Tomaselli K.J. Litwack G. Alnemri E.S. Proc. Natl. Acad. Sci. U. S. A. 1996; 93: 7464-7469Crossref PubMed Scopus (693) Google Scholar). Taken together, indicate that αB-crystallin the cytochrome and activation of caspase-3 by inhibiting the autoproteolytic maturation of its p24 intermediate. αB-crystallin binds to caspase-3 in we αB-crystallin from cells cell from or cells with shown in αB-crystallin with the p24 partially processed caspase-3 by an in cells this in the caspase-3 processing intermediate that with αB-crystallin is the as the p24 partially processed caspase-3 in cytosolic extracts treated with cytochrome or caspase-8 in the presence of αB-crystallin the p24 intermediate is abundant procaspase-3 in cell it with αB-crystallin in the of between αB-crystallin and thereby the of the between αB-crystallin and partially processed caspase-3 in vivo. These that αB-crystallin antagonizes the autocatalytic processing of caspase-3 by binding to and inhibiting the partially processed protease. Recent studies indicate that several HSPs inhibit the mitochondrial apoptotic pathway by specifically binding to components of the cell death and disrupting the of the Hsp70 and Hsp90 bind to Apaf-1, Hsp27 binds to cytochrome c to prevent the cytochrome of Apaf-1 and activation of procaspase-9 (13Beere H.M. Wolf B.B. Cain K. Mosser D.D. Mahboubi A. Kuwana T. Tailor P. Morimoto R.I. Cohen G.M. Green D.R. Nat. Cell Biol. 2000; 2: 469-475Crossref PubMed Scopus (1289) Google Scholar, 14Pandey P. Saleh A. Nakazawa A. Kumar S. Srinivasula S.M. Kumar V. Weichselbaum R. Nalin C. Alnemri E.S. Kufe D. Kharbanda S. EMBO J. 2000; 19: 4310-4322Crossref PubMed Scopus (489) Google Scholar, 15Saleh A. Srinivasula S.M. Balkir L. Robbins P.D. Alnemri E.S. Nat. Cell Biol. 2000; 2: 476-483Crossref PubMed Scopus (737) Google Scholar, J.M. Ducasse C. Bonniaud P. Ravagnan L. Susin S.A. Diaz-Latoud C. Gurbuxani S. Arrigo A.P. Kroemer G. Solary E. Garrido C. Nat. Cell Biol. 2000; 2: 645-652Crossref PubMed Scopus (834) Google Scholar). We demonstrate here that the small HSP αB-crystallin inhibits both the mitochondrial and death receptor apoptotic pathways by a novel αB-crystallin binds to caspase-3 that has been partially processed by caspase-9 or caspase-8 cleavage and inhibits the autoproteolytic of its prodomain to produce its large this autocatalytic maturation is caspase-3 activation by both the mitochondrial and death receptor pathways, the of caspase-3 maturation by αB-crystallin is a to inhibit both pathways. In contrast, Hsp70 inhibits the mitochondrial pathway and cells to apoptosis (13Beere H.M. Wolf B.B. Cain K. Mosser D.D. Mahboubi A. Kuwana T. Tailor P. Morimoto R.I. Cohen G.M. Green D.R. Nat. Cell Biol. 2000; 2: 469-475Crossref PubMed Scopus (1289) Google Scholar, 15Saleh A. Srinivasula S.M. Balkir L. Robbins P.D. Alnemri E.S. Nat. Cell Biol. 2000; 2: 476-483Crossref PubMed Scopus (737) Google J. 1997; Google Scholar). neither Hsp27 nor Hsp70 effect on the autoproteolytic maturation of caspase-3. These indicate that αB-crystallin inhibits apoptosis by a novel that is distinct from that of HSPs examined to the autoproteolytic maturation of is also inhibited by the conserved family member αB-crystallin, inhibit the cleavage of procaspase-3 by caspase-8 in cytosolic it binds to the p24 partially processed caspase-3 and inhibits its autoproteolytic maturation Q.L. Roy N. Stennicke H.R. Van Arsdale T. Zhou Q. Srinivasula S.M. Alnemri E.S. Salvesen G.S. Reed J.C. EMBO J. 1998; 17: 2215-2223Crossref PubMed Scopus (1242) Google Scholar). αB-crystallin is in this its of autoproteolytic maturation is at as by of αB-crystallin in cell we have the of αB-crystallin in some For instance, α-crystallin protein of αB-crystallin and of the protein in the lens, and αB-crystallin as as of the protein in muscle (18Clark J.I. Muchowski P.J. Curr. Opin. Struct. Biol. 2000; 10: 52-59Crossref PubMed Scopus (220) Google Scholar, 19Kato K. Shinohara H. Kurobe N. Inaguma Y. Shimizu K. Ohshima K. Biochim. Biophys. Acta. 1991; 1074: 201-208Crossref PubMed Scopus (188) Google Scholar). However, is also a of active and Q.L. Roy N. Stennicke H.R. Van Arsdale T. Zhou Q. Srinivasula S.M. Alnemri E.S. Salvesen G.S. Reed J.C. EMBO J. 1998; 17: 2215-2223Crossref PubMed Scopus (1242) Google Scholar, Q.L. R. Salvesen G.S. Reed J.C. 1997; PubMed Scopus Google αB-crystallin is by caspases the molecular by which αB-crystallin inhibits the autoproteolytic maturation of is to from that of the small HSP family members αB-crystallin and Hsp27 inhibit apoptosis by largely distinct In our Hsp27 the activation of as others have (16Bruey J.M. Ducasse C. Bonniaud P. Ravagnan L. Susin S.A. Diaz-Latoud C. Gurbuxani S. Arrigo A.P. Kroemer G. Solary E. Garrido C. Nat. Cell Biol. 2000; 2: 645-652Crossref PubMed Scopus (834) Google αB-crystallin inhibits this Moreover, Hsp27 inhibit the autoproteolytic maturation of caspase-3. αB-crystallin and Hsp27 of the are their α-crystallin the and are largely divergent (18Clark J.I. Muchowski P.J. Curr. Opin. Struct. Biol. 2000; 10: 52-59Crossref PubMed Scopus (220) Google Scholar). the anti-apoptotic mechanisms of closely related small HSPs are to the of their distinct we and others (21Mehlen P. Kretz-Remy C. Preville X. Arrigo A.P. EMBO J. 1996; 15: 2695-2706Crossref PubMed Scopus (518) Google Scholar, 22Mehlen P. Schulze-Osthoff K. Arrigo A.P. J. Biol. Chem. 1996; 271: 16510-16514Abstract Full Text Full Text PDF PubMed Scopus (582) Google have that Hsp27, αB-crystallin, inhibits both the mitochondrial and death receptor apoptotic pathways, the by which Hsp27 inhibits the is In our Hsp27 inhibit the activation of that Hsp27 inhibits death receptor apoptosis of this by with procaspase-8 our evidence that αB-crystallin and Hsp27 inhibit apoptosis by distinct In to αB-crystallin, two HSPs have been shown to caspase-3 maturation S. Roy S. D. T. Y. R. P. R. A. EMBO J. PubMed Scopus Google Scholar, A. J. S. EMBO J. PubMed Scopus Google Scholar). and procaspase-3 form a multimeric complex in the mitochondria of In cytosolic and promote the proteolytic activation of procaspase-3 by caspase-8 and in an that their the of procaspase-3 to proteolytic cleavage by apical with our that αB-crystallin inhibits the autocatalytic maturation of indicate that the proteolytic maturation of caspase-3 is an In αB-crystallin is a novel negative regulator of apoptosis that acts distally in the conserved cell death of by disrupting the autoproteolytic maturation of caspase-3. the of αB-crystallin in the and in αB-crystallin is to a particularly in apoptosis in the that a in αB-crystallin a by and the of αB-crystallin in the and in muscle P. A. P. Z. A. D. F. F. D. M. Nat. 1998; PubMed Scopus Google Scholar). the of cells into is by an apoptotic that to the of the and from cells that the of the Y. J. Cell Biol. 1998; PubMed Scopus Google Scholar, S. D. J. Cell Biol. 1997; PubMed Scopus Google Scholar). αB-crystallin is expressed in it is to that its presence the of the apoptotic and the of In our a of For instance, function in αB-crystallin's anti-apoptotic of Hsp27 is its anti-apoptotic T. M. Preville X. A. G. Ducasse C. C. M. Arrigo A.P. J. M. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google the of in αB-crystallin's anti-apoptotic has been These and examined in studies of αB-crystallin that are in one or more of We active caspase-8 and and Peter their critical of the
Kamradt et al. (Tue,) studied this question.