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BAG-1 proteins protect cardiac myocytes from simulated ischemia/reperfusion-induced apoptosis via an alternate mechanism of cell survival independent of the proteasome

BAG-1 proteins protect cardiac myocytes from simulated ischemia/reperfusion-induced apoptosis via an alternate mechanism of cell survival independent of the proteasome
BAG-1 proteins protect cardiac myocytes from simulated ischemia/reperfusion-induced apoptosis via an alternate mechanism of cell survival independent of the proteasome
BAG-1 (Bcl-2-associated athanogene-1) proteins interact with the HSC70 and HSP70 heat shock proteins and have been proposed to promote cell survival by coordinating the function of these chaperones with the proteasome to facilitate protein degradation. Consistent with this proposal, previous analyses in cancer cells have demonstrated that BAG-1 requires protein domains important for HSC70/HSP70 and proteasome binding in order to interfere with the growth inhibition induced by heat shock (Townsend, P. A., Cutress, R. I., Sharp, A., Brimmell, M., and Packham, G. (2003) Cancer Res., 63, 4150–4157). Moreover, cellular stress triggered the relocalization of the cytoplasmic BAG-1S (36 kDa) isoform to the nucleus, and both BAG-1S and the constitutively nuclear localized BAG-1L (50 kDa) isoform suppressed heat shock-induced apoptosis to the same extent, suggesting a critical role in the nucleus. Because ischemia (I) and reperfusion (R) are important stress signals in acute and chronic heart disease, we have examined the expression and function of BAG-1 proteins in primary cardiac myocytes (CMs) and the Langendorff-perfused intact heart. The expression of both BAG-1 isoforms, BAG-1S and BAG-1L, was rapidly induced following ischemia in rat CM, and this was maintained during subsequent reperfusion. In control hearts, BAG-1S and BAG-1L were readily detectable in both the nucleus and the cytoplasm. However, BAG-1S did not relocate to the nucleus following simulated I/R. BAG-1 interacted with both RAF-1 and HSC70 in CMs and the whole heart, and binding to HSC70 was increased following I/R. Overexpression of the human BAG-1S and BAG-1 M isoforms significantly reduced CM apoptosis following simulated I/R. By contrast, BAG-1L or BAG-1S fused to a heterologous nuclear localization sequence failed to protect CM. Finally, overexpression of BAG-1 deletion and point mutants unable to bind HSC70/HSP70 failed to offer cardioprotection. Surprisingly, a deletion mutant lacking the N-terminal ubiquitin-like domain, which mediates interaction with the proteasome, still promoted cardioprotection. Therefore, BAG-1 has a novel cardioprotective role, mediated via association with HSC70/HSP70, which is critical upon cytoplasmic localization but independent of the BAG-1 ubiquitin-like domain. Our studies demonstrate that BAG-1 can influence cellular response to stress by multiple mechanisms, potentially influenced by the cell type and nature of the stress signal.
0021-9258
20723-20728
Townsend, Paul A.
a2680443-664e-46d0-b4dd-97456ba810db
Cutress, Ramsey I.
68ae4f86-e8cf-411f-a335-cdba51797406
Carroll, Christopher J.
83f87248-a322-4c00-b0e0-a54119376c26
Lawrence, Kevin M.
ff8347b7-930c-4414-beab-65f6d6514b73
Scarabelli, Tiziano M.
ac96a777-880e-4e39-9884-f11a0978da35
Packham, Graham
fdabe56f-2c58-469c-aadf-38878f233394
Stephanou, Anastasis
e9d502e8-693c-4458-a3c6-5e2844665db3
Latchman, David S.
71e9db7c-9075-4b49-afac-6413085378db
Townsend, Paul A.
a2680443-664e-46d0-b4dd-97456ba810db
Cutress, Ramsey I.
68ae4f86-e8cf-411f-a335-cdba51797406
Carroll, Christopher J.
83f87248-a322-4c00-b0e0-a54119376c26
Lawrence, Kevin M.
ff8347b7-930c-4414-beab-65f6d6514b73
Scarabelli, Tiziano M.
ac96a777-880e-4e39-9884-f11a0978da35
Packham, Graham
fdabe56f-2c58-469c-aadf-38878f233394
Stephanou, Anastasis
e9d502e8-693c-4458-a3c6-5e2844665db3
Latchman, David S.
71e9db7c-9075-4b49-afac-6413085378db

Townsend, Paul A., Cutress, Ramsey I., Carroll, Christopher J., Lawrence, Kevin M., Scarabelli, Tiziano M., Packham, Graham, Stephanou, Anastasis and Latchman, David S. (2004) BAG-1 proteins protect cardiac myocytes from simulated ischemia/reperfusion-induced apoptosis via an alternate mechanism of cell survival independent of the proteasome. The Journal of Biological Chemistry, 279 (20), 20723-20728. (doi:10.1074/jbc.M400399200). (PMID:14978028)

Record type: Article

Abstract

BAG-1 (Bcl-2-associated athanogene-1) proteins interact with the HSC70 and HSP70 heat shock proteins and have been proposed to promote cell survival by coordinating the function of these chaperones with the proteasome to facilitate protein degradation. Consistent with this proposal, previous analyses in cancer cells have demonstrated that BAG-1 requires protein domains important for HSC70/HSP70 and proteasome binding in order to interfere with the growth inhibition induced by heat shock (Townsend, P. A., Cutress, R. I., Sharp, A., Brimmell, M., and Packham, G. (2003) Cancer Res., 63, 4150–4157). Moreover, cellular stress triggered the relocalization of the cytoplasmic BAG-1S (36 kDa) isoform to the nucleus, and both BAG-1S and the constitutively nuclear localized BAG-1L (50 kDa) isoform suppressed heat shock-induced apoptosis to the same extent, suggesting a critical role in the nucleus. Because ischemia (I) and reperfusion (R) are important stress signals in acute and chronic heart disease, we have examined the expression and function of BAG-1 proteins in primary cardiac myocytes (CMs) and the Langendorff-perfused intact heart. The expression of both BAG-1 isoforms, BAG-1S and BAG-1L, was rapidly induced following ischemia in rat CM, and this was maintained during subsequent reperfusion. In control hearts, BAG-1S and BAG-1L were readily detectable in both the nucleus and the cytoplasm. However, BAG-1S did not relocate to the nucleus following simulated I/R. BAG-1 interacted with both RAF-1 and HSC70 in CMs and the whole heart, and binding to HSC70 was increased following I/R. Overexpression of the human BAG-1S and BAG-1 M isoforms significantly reduced CM apoptosis following simulated I/R. By contrast, BAG-1L or BAG-1S fused to a heterologous nuclear localization sequence failed to protect CM. Finally, overexpression of BAG-1 deletion and point mutants unable to bind HSC70/HSP70 failed to offer cardioprotection. Surprisingly, a deletion mutant lacking the N-terminal ubiquitin-like domain, which mediates interaction with the proteasome, still promoted cardioprotection. Therefore, BAG-1 has a novel cardioprotective role, mediated via association with HSC70/HSP70, which is critical upon cytoplasmic localization but independent of the BAG-1 ubiquitin-like domain. Our studies demonstrate that BAG-1 can influence cellular response to stress by multiple mechanisms, potentially influenced by the cell type and nature of the stress signal.

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Published date: 14 May 2004

Identifiers

Local EPrints ID: 26644
URI: http://eprints.soton.ac.uk/id/eprint/26644
ISSN: 0021-9258
PURE UUID: 253ae87c-665f-4e44-8aaa-ca8789607dd9
ORCID for Graham Packham: ORCID iD orcid.org/0000-0002-9232-5691

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Date deposited: 21 Apr 2006
Last modified: 16 Mar 2024 03:14

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Contributors

Author: Paul A. Townsend
Author: Christopher J. Carroll
Author: Kevin M. Lawrence
Author: Tiziano M. Scarabelli
Author: Graham Packham ORCID iD
Author: Anastasis Stephanou
Author: David S. Latchman

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