Protein kinase A-catalyzed phosphorylation of heat shock protein 60 chaperone regulates its attachment to histone 2B in the T lymphocyte plasma membrane.
Accumulating evidence suggests that the mitochondrial molecular chaperone heat shock protein 60 (hsp60) also can localize in extramitochondrial sites. However, direct evidence that hsp60 functions as a chaperone outside of mitochondria is presently lacking. A 60-kDa protein that is present in the plasma membrane of a human leukemic CD4(+) CEM-SS T cell line and is phosphorylated by protein kinase A (PKA) was identified as hsp60. An 18-kDa plasma membrane-associated protein coimmunoprecipitated with hsp60 and was identified as histone 2B (H2B). Hsp60 physically associated with H2B when both molecules were in their dephospho forms. By contrast, PKA-catalyzed phosphorylation of both hsp60 and H2B caused dissociation of H2B from hsp60 and loss of H2B from the plasma membrane of intact T cells. These results suggest that (i) hsp60 and H2B can localize in the T cell plasma membrane; (ii) hsp60 functions as a molecular chaperone for H2B; and (iii) PKA-catalyzed phosphorylation of both hsp60 and H2B appears to regulate the attachment of H2B to hsp60. We propose a model in which phosphorylation/dephosphorylation regulates chaperoning of H2B by hsp60 in the plasma membrane.
Department of Internal Medicine, Wake Forest University School of Medicine, Winston-Salem, N. C. 27157, Canada.
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Khan
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Wallin
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Gupta
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Kammer
D000595:Amino Acid Sequence; D015496:CD4-Positive T-Lymphocytes / Q000378:metabolism; D002384:Catalysis; D002462:Cell Membrane / Q000378:metabolism; D018834:Chaperonin 60 / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D006657:Histones / Q000378:metabolism*; D006801:Humans; D013058:Mass Spectrometry; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D010449:Peptide Mapping; D010766:Phosphorylation; D011233:Precipitin Tests; D011994:Recombinant Proteins / Q000378:metabolism; D014407:Tumor Cells, Cultured
D018834:Chaperonin 60; D006657:Histones; D011994:Recombinant Proteins; D017868:Cyclic AMP-Dependent Protein Kinases