title: Phosphorylation of the heat shock-related protein, HSP20, mediates cyclic nucleotide-dependent relaxation.
abstract: Cyclic nucleotide-dependent relaxation of vascular smooth muscle is associated with increases in the phosphorylation of the small heat shock-related protein, HSP20. To determine whether phosphorylated HSP20 directly mediates relaxation, we used gene transfection and protein transduction of HSP20 analogues. Rat mesangial cells were transfected with constructs containing wild-type HSP20-enhanced green fluorescent protein (EGFP), phosphorylation site mutated HSP20 (S16A-HSP20-EGFP), or EGFP alone. Contractile properties were determined on a silicone polymer substrata. In the presence of serum, EGFP-vector transfected control cells and S16A-HSP20 transfected cells formed wrinkles on the polymer (contracted). Activation of cyclic nucleotide signaling pathways in the EGFP-vector transfected control cells led to a time-dependent decrease in the wrinkles (relaxation). The S16A-HSP20 transfected cells were refractory to cyclic nucleotide-dependent relaxation. Cells overexpressing the wild-type HSP20 did not form wrinkles on the polymer in response to serum (refractory to contraction). Treatment of precontracted strips of intact bovine carotid artery smooth muscle with synthetic peptides containing HIV-trans-activating transcriptional activator and a phosphopeptide motif of HSP20 led to dose-dependent relaxation. These data provide evidence that phosphorylated HSP20 has a direct role in smooth muscle relaxation and that small phosphopeptide motifs of HSP20 can mimic the effects of the entire molecule.
authors.affiliation: Department of Radiology, Mayo Clinic, Rochester, MN, USA.
authors.forename: David
authors.initials: D
authors.lastname: Woodrum
authors.forename: Walter
authors.initials: W
authors.lastname: Pipkin
authors.forename: Deron
authors.initials: D
authors.lastname: Tessier
authors.forename: Padmini
authors.initials: P
authors.lastname: Komalavilas
authors.forename: Colleen M
authors.initials: CM
authors.lastname: Brophy
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D005455:Fluorescent Antibody Technique; D005920:Glomerular Mesangium / Q000166:cytology; D050886:HSP20 Heat-Shock Proteins; D006360:Heat-Shock Proteins / Q000378:metabolism*; D009126:Muscle Relaxation / Q000502:physiology*; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D009712:Nucleotides, Cyclic / Q000502:physiology*; D010710:Phosphates / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D051381:Rats; D015398:Signal Transduction; D014162:Transfection
chemical_list: D050886:HSP20 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D009712:Nucleotides, Cyclic; D010710:Phosphates; D010750:Phosphoproteins