The small heat shock-related protein, HSP20, is a cAMP-dependent protein kinase substrate that is involved in airway smooth muscle relaxation.
Activation of the cAMP/cAMP-dependent PKA pathway leads to relaxation of airway smooth muscle (ASM). The purpose of this study was to examine the role of the small heat shock-related protein HSP20 in mediating PKA-dependent ASM relaxation. Human ASM cells were engineered to constitutively express a green fluorescent protein-PKA inhibitory fusion protein (PKI-GFP) or GFP alone. Activation of the cAMP-dependent signaling pathways by isoproterenol (ISO) or forskolin led to increases in the phosphorylation of HSP20 in GFP but not PKI-GFP cells. Forskolin treatment in GFP but not PKI-GFP cells led to a loss of central actin stress fibers and decreases in the number of focal adhesion complexes. This loss of stress fibers was associated with dephosphorylation of the actin-depolymerizing protein cofilin in GFP but not PKI-GFP cells. To confirm that phosphorylated HSP20 plays a role in PKA-induced ASM relaxation, intact strips of bovine ASM were precontracted with serotonin followed by ISO. Activation of the PKA pathway led to relaxation of bovine ASM, which was associated with phosphorylation of HSP20 and dephosphorylation of cofilin. Finally, treatment with phosphopeptide mimetics of HSP20 possessing a protein transduction domain partially relaxed precontracted bovine ASM strips. In summary, ISO-induced phosphorylation of HSP20 or synthetic phosphopeptide analogs of HSP20 decreases phosphorylation of cofilin and disrupts actin in ASM, suggesting that one possible mechanism by which HSP20 mediates ASM relaxation is via regulation of actin filament dynamics.
Komalavilas
Padmini
P
Center for Metabolic Biology, College of Liberal Arts and Sciences, Arizona State University, PO Box 873704, Tempe, AZ 85287-3704, USA. padmini.komalavilas@asu.edu
Penn
Raymond B
RB
Flynn
Charles R
CR
Thresher
Jeffrey
J
Lopes
Luciana B
LB
Furnish
Elizabeth J
EJ
Guo
Manhong
M
Pallero
Manuel A
MA
Murphy-Ullrich
Joanne E
JE
Brophy
Colleen M
CM
D000818:Animals; D002417:Cattle; D005576:Colforsin / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D050886:HSP20 Heat-Shock Proteins / Q000378:metabolism*; D007545:Isoproterenol / Q000494:pharmacology; D007700:Kinetics; D009126:Muscle Relaxation / Q000187:drug effects / Q000502:physiology*; D009130:Muscle, Smooth / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*; D010748:Phosphopeptides / Q000378:metabolism; D012143:Respiratory Physiological Phenomena; D012701:Serotonin / Q000494:pharmacology
D050886:HSP20 Heat-Shock Proteins; C494382:HSPB6 protein, human; D010748:Phosphopeptides; D005576:Colforsin; D012701:Serotonin; D017868:Cyclic AMP-Dependent Protein Kinases; D007545:Isoproterenol