Specific Regulation of Noncanonical p38α Activation by Hsp90-Cdc37 Chaperone Complex in Cardiomyocyte

Abstract

Rationale: p38 is an important stress activated protein kinase involved in gene regulation, proliferation, differentiation, and cell death regulation in heart. p38 kinase activity can be induced through canonical pathway via upstream kinases or by noncanonical autophosphorylation. The intracellular p38 kinase activity is tightly regulated and maintained at low level under basal condition. The underlying regulatory mechanism for canonical p38 kinase activation is well-studied, but the regulation of noncanonical p38 autophosphorylation remains poorly understood. Objective: We investigated the molecular basis for the regulation of noncanonical p38 autophosphorylation and its potential functional impact in cardiomyocytes. Methods and Results: Using both proteomic and biochemical tools, we established that heat shock protein (Hsp)90-Cdc37 chaperones are part of the p38␣ signaling complex in mammalian cells both in vitro and in vivo. The Hsp90-Cdc37 chaperone complex interacts with p38 via direct binding between p38 and Cdc37. Cdc37 expression is both sufficient and necessary to suppress noncanonical p38 activation via autophosphorylation at either basal state or under TAB1 (TAK1 binding protein-1) induction. In contrast, Cdc37 expression has no impact on p38 activation by canonical upstream kinase MKK3 or oxidative stress. Furthermore, Hsp90 inhibition results in p38 activation via autophosphorylation, and p38 activity contribute to apoptotic cell death induced by Hsp90 inhibition. Conclusion: Our study has revealed a so far uncharacterized function of Hsp90-Cdc37 as an endogenous regulator of noncanonical p38 activity. (Circ Res. 2010;106:1404-1412.)Key Words: p38 mitogen-activated protein kinase Ⅲ noncanonical pathway Ⅲ Hsp90 Ⅲ Cdc37 Ⅲ autophosphorylation O xidative stress, proinflammatory cytokines and many other extracellular stimuli activate intracellular stress responses through stress signaling pathways, including SAPK (stress-activated protein kinase) p38 as a member of the mitogen-activated protein kinase (MAPK) superfamily. [1][2][3][4][5] Although the role of p38 in heart remains controversial, activation of p38 in response to ischemia/reperfusion has been demonstrated repetitively. Several findings suggest p38␣ contributes to myocyte cell death by promoting production of proinflammatory cytokines including tumor necrosis factor (TNF)␣, interleukin (IL)-1, and IL-8. This is also supported by the protective effect of p38-specific inhibitor SB203580 in ischemia. On the other hand, protective effect of p38 through activation of heat shock protein (Hsp)27 has also been suggested. There are 2 modes of p38 activation in ischemia. One is the canonical p38 pathway, which is activated by a cascade of phosphorylation through upstream MEKKs (MAPK/extracellular-activated kinase kinases) such as Ask1, 6 and MAPK kinase (MKK)3, -4, or -6, leading to phosphorylation of the TGY motif within the p38 activation loop. 3,4,7 In addition, noncanonical MKK-independent activation of p38 has been demonstrated through intrinsic au...

New Therapeutic Targets in Cardiology

“…28 In addition to the archetypal canonical activation by MKKs and the alternate TAB1-mediated autoactivation reviewed above, there are a variety of other pathways that modulate p38 activity. These include phosphatases that dephosphorylate the TGY motif, 36 G-protein-coupled receptor kinase 2 that disrupts the docking of MKKs by phosphorylating a threonine residue on p38, 37 a heat shock protein 90-cdc37 chaperone that stabilizes p38 preventing activation by TAB1, 38 and the acetylation of a lysine that increases p38's affinity for ATP. 39 The presence of numerous mechanisms modulating p38 activity is a likely testament of the need to exquisitely control this crucial kinase.…”

p38αMAPK interacts with and inhibits RARα: suppression of the kinase enhances the therapeutic activity of retinoids in acute myeloid leukemia cells

“…The following plasmid constructs were used: hRARa and PML-RARa; 23 hRARaS77A (S77A), 19 hRARaS369A (S369A); 28 hRARaL342T (L342T) and hRARaP345G/D346A (P345G/D346A); 22 hPML-RARaS581A (S581A, obtained by site-directed mutagenesis using standard methods was inserted in PSG5); hPML-RARaS873A (S873A); 10 p38aMAPK (p38a); 19 KRSPA Flag p38 (dnP38); 19 GST-p38a andGST-DNp38a; 29 HA-WTp38a and HA-Y258A-p38a (kind gifts from S Keyse and R Dickinson, Dundee, UK); HA-I116A-p38a and HA-Q120A-p38a (kind gifts from EJ Goldsmith, Dallas, TX, USA); Flag-p38a(CD mut ) (mCD), 30 Flag-p38a(ED mut ) (mED), 30 b2RARE-luc and DR5-tk-luc;…”

Effect of pressure overload-induced hypertrophy on the expression and localization of p38 MAP kinase isoforms in the mouse heart

“…In addition, there exists at least 3 means whereby p38 activation is independent of MKK activity. Interactions with TAB1 or ZAP-70 [6,7] induce autophosphorylation of p38 within the activation loop whereas interactions with Hsp90-Cdc37 supressed this autophosphorylation [8]. Although the exact role of each p38 isoform remains to be determined, each p38 isoform has been independently knocked out in mice: p38α-deficient mice show embryonic lethality due to placental defects, whereas p38β-, p38γ-, and p38δ-null mice appear to have normal phenotypes [9].…”