Inactivation of dual-specificity phosphatases is involved in the regulation of extracellular signal-regulated kinases by heat shock and hsp72.
Extracellular signal-regulated kinase 1 (ERK1) and ERK2 (ERK1/2) dramatically enhance survival of cells exposed to heat shock. Using Cos-7 cells and primary human fibroblasts (IMR90 cells), we demonstrated that heat shock activates ERKs via two distinct mechanisms: stimulation of the ERK-activating kinases, MEK1/2, and inhibition of ERK dephosphorylation. Under milder heat shock conditions, activation of ERKs proceeded mainly through stimulation of MEK1/2, whereas under more severe heat shock MEK1/2 could no longer be activated and the inhibition of ERK phosphatases became critical. In Cos-7 cells, nontoxic heat shock caused rapid inactivation of the major ERK phosphatase, MKP-3, by promoting its aggregation, so that in cells exposed to 45 degrees C for 20 min, 90% of MKP-3 became insoluble. MKP-3 aggregation was reversible and, 1 h after heat shock, MKP-3 partially resolubilized. The redistribution of MKP-3 correlated with an increased rate of ERK dephosphorylation. Similar heat-induced aggregation, followed by partial resolubilization, was found with a distinct dual-specificity phosphatase MKP-1 but not with MKP-2. Therefore, MKP-3 and MKP-1 appeared to be critical heat-labile phosphatases involved in the activation of ERKs by heat shock. Expression of the major heat shock protein Hsp72 inhibited activation of MEK1/2 and prevented inactivation of MKP-3 and MKP-1. Hsp72DeltaEEVD mutant lacking a chaperone activity was unable to protect MKP-3 from heat inactivation but interfered with MEK1/2 activation similar to normal Hsp72. Hence, Hsp72 suppressed ERK activation by both protecting dual-specificity phosphatases, which was dependent on the chaperone activity, and suppressing MEK1/2, which was independent of the chaperone activity.
Yaglom
Julia
J
Department of Biochemistry, Boston University School of Medicine, Boston, Massachusetts 02118, USA.
O'Callaghan-Sunol
Cornelia
C
Gabai
Vladimir
V
Sherman
Michael Y
MY
D000818:Animals; D019556:COS Cells; D002449:Cell Aggregation; D018797:Cell Cycle Proteins; D002458:Cell Fractionation; D054638:Dual Specificity Phosphatase 1; D004789:Enzyme Activation; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D050884:HSP72 Heat-Shock Proteins; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006358:Hot Temperature; D006801:Humans; D017874:Immediate-Early Proteins / Q000378:metabolism; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D054645:Protein Phosphatase 1; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D013379:Substrate Specificity; D014466:Ultraviolet Rays
D018797:Cell Cycle Proteins; D050884:HSP72 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D017874:Immediate-Early Proteins; C482128:MAP2K2 protein, human; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D020928:Mitogen-Activated Protein Kinases; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; C482125:MAP2K1 protein, human; D020929:Mitogen-Activated Protein Kinase Kinases; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D010744:Phosphoric Monoester Hydrolases; C517019:DUSP1 protein, human; D054638:Dual Specificity Phosphatase 1; D017027:Protein Tyrosine Phosphatases