title: The small heat shock protein (HSP) 20 is dynamically associated with the actin cross-linking protein actinin.
abstract: BACKGROUND
  The heat shock-related protein (HSP) 20 is associated with actin and modulates smooth-muscle relaxation. We hypothesized that HSP20 mediates vasorelaxation via dynamic interactions with cytoskeletal proteins, such as actin, or actin binding proteins, such as alpha-actinin.
  
  
  METHODS
  Physiological responses of strips of bovine carotid artery were analyzed with a muscle bath. In other experiments, the arteries were homogenized, and imunoprecipitations were performed. Immunohistochemistry with anti-HSP20 and anti-actinin antibodies was used to determine co-localization of the two proteins.
  
  
  RESULTS
  Bovine carotid arteries contracted in response to serotonin and rapidly relaxed in response to forskolin. HSP20 co-immunoprecipitated with both actin and alpha-actinin, but not with HSP27 or paxillin. Immunostaining with HSP20 and alpha-actinin antibodies demonstrated that HSP20 and alpha-actinin co-localized. The amount of HSP20 that immunoprecipitated with alpha -actinin was markedly diminished in muscles that were treated with the vasorelaxant forskolin.
  
  
  CONCLUSIONS
  HSP20 is associated with both actin and alpha-actinin. Activation of cyclic nucleotide-dependent signaling pathways leads to increases in the phosphorylation of HSP20 and a decrease in the association of HSP20 with alpha-actinin. These data suggest that phosphorylation of HSP20 may lead to relaxation of vascular smooth muscles through a dynamic association with cytoskeletal elements.
authors.affiliation: Department of Surgery, Division of Vascular Surgery, Mayo Clinic Scottsdale, Scottsdale, AZ, USA.
authors.forename: Deron J
authors.initials: DJ
authors.lastname: Tessier
authors.forename: Padmini
authors.initials: P
authors.lastname: Komalavilas
authors.forename: Alyssa
authors.initials: A
authors.lastname: Panitch
authors.forename: Lokesh
authors.initials: L
authors.lastname: Joshi
authors.forename: Colleen M
authors.initials: CM
authors.lastname: Brophy
mesh_terms: D000185:Actinin / Q000032:analysis* / Q000378:metabolism; D000199:Actins / Q000032:analysis; D000818:Animals; D002339:Carotid Arteries; D002417:Cattle; D005576:Colforsin / Q000494:pharmacology; D050886:HSP20 Heat-Shock Proteins; D006360:Heat-Shock Proteins / Q000032:analysis* / Q000378:metabolism; D007150:Immunohistochemistry; D007163:Immunosorbent Techniques; D009119:Muscle Contraction / Q000187:drug effects; D009126:Muscle Relaxation / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000737:chemistry* / Q000502:physiology; D010750:Phosphoproteins / Q000032:analysis* / Q000378:metabolism; D010766:Phosphorylation; D012701:Serotonin / Q000494:pharmacology
chemical_list: D000199:Actins; D050886:HSP20 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D010750:Phosphoproteins; D000185:Actinin; D005576:Colforsin; D012701:Serotonin