The small heat shock-related protein, HSP20, is phosphorylated on serine 16 during cyclic nucleotide-dependent relaxation.
The small heat shock-related protein 20 (HSP20) is present in four isoforms in bovine carotid artery smooth muscles. Three of the isoforms are phosphorylated and one is not. Increases in the phosphorylation of two isoforms of HSP20 (isoform 3, pI 5.9; and 8, pI 5.7) are associated with cyclic nucleotide-dependent relaxation of bovine carotid artery smooth muscles. Increases in the phosphorylation of another isoform (isoform 4, pI 6.0) are associated with phorbol ester-induced contraction of bovine carotid artery smooth muscles. In this investigation we determined that isoforms 3 and 8 are phosphorylated on Ser16 of the HSP20 molecule during activation of cAMP-dependent signaling pathways. Phosphorylation state-specific antibodies produced against a peptide containing phosphorylated Ser16 recognized isoforms 3 and 8 but not isoform 4. In human vascular tissue, only isoform 3 is present. Incubation of transiently permeabilized strips of bovine carotid artery smooth muscle with synthetic peptides in which Ser16 is phosphorylated, inhibits contractile responses to high extracellular KCl and to serotonin. These data suggest that phosphorylation of HSP20 on Ser16 modulates cAMP-dependent vasorelaxation.
Beall
A
A
Department of Medicine (Institute for Molecular Medicine and Genetics), Medical College of Georgia, Augusta, Georgia 30912, USA.
Bagwell
D
D
Woodrum
D
D
Stoming
T A
TA
Kato
K
K
Suzuki
A
A
Rasmussen
H
H
Brophy
C M
CM
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002417:Cattle; D000242:Cyclic AMP / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D017869:Cyclic GMP-Dependent Protein Kinases / Q000378:metabolism; D017931:DNA Primers; D050886:HSP20 Heat-Shock Proteins; D006360:Heat-Shock Proteins / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D008969:Molecular Sequence Data; D009119:Muscle Contraction / Q000187:drug effects; D009126:Muscle Relaxation / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D010455:Peptides / Q000494:pharmacology; D010750:Phosphoproteins / Q000737:chemistry / Q000378:metabolism*; D010766:Phosphorylation; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012694:Serine / Q000378:metabolism*
D017931:DNA Primers; D050886:HSP20 Heat-Shock Proteins; C494382:HSPB6 protein, human; D006360:Heat-Shock Proteins; D010455:Peptides; D010750:Phosphoproteins; D011994:Recombinant Proteins; D012694:Serine; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D017869:Cyclic GMP-Dependent Protein Kinases