Calcium-independent contraction and sensitization of airway smooth muscle by p21-activated protein kinase

P. K. McFawn, L. Shen, S. G. Vincent, A. Mak, J. E. Van Eyk, J. T. Fisher

Research output: Contribution to journalArticle

Abstract

In Triton-skinned phasic ileal smooth muscle, constitutively active recombinant p21-activated kinase (PAK3) has been shown to induce Ca2+-independent contraction, which is accompanied by phosphorylation of caldesmon and desmin (Van Eyk JE, Arrell DK, Foster DB, Strauss JD, Heinonen TY, Furmaniak-Kazmierczak E, Cote GP, and Mak AS. J Biol Chem 273: 23433-23439, 1998). In the present study, we investigated whether PAK has a broad impact on smooth muscle in general by testing the hypothesis that PAK induces Ca2+-independent contractions and/or Ca2+ sensitization in tonic airway smooth muscle and that the process is mediated via phosphorylation of caldesmon. In the absence of Ca2+ (pCa > 9), constitutively active glutathione-S-transferase-murine PAK3 (GST-mPAK3) caused force generation of Triton-skinned canine tracheal smooth muscle (TSM) fibers to ∼40% of the maximal force generated by Ca2+ at pCa 4.4. In addition, GST-mPAK3 enhanced Ca2+ sensitivity of contraction by increasing force generation by 80% at intermediate Ca2+ concentrations (pCa 6.2), whereas it had no effect at pCa 4.4. Catalytically inactive GST-mPAK3K297R had no effect on force production. Using antibody against one of the PAK-phosphorylated sites (Ser657) on caldesmon, we showed that a basal level of phosphorylation of caldesmon occurs at this site in skinned TSM and that PAK-induced contraction was accompanied by a significant increase in the level of phosphorylation. Western blot analyses show that PAK1 is the predominant PAK isoform expressed in murine, rat, canine, and porcine TSM. We conclude that PAK causes Ca2+-independent contractions and produces Ca2+ sensitization of skinned phasic and tonic smooth muscle, which involves an incremental increase in caldesmon phosphorylation.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Lung Cellular and Molecular Physiology
Volume284
Issue number5 28-5
StatePublished - May 1 2003
Externally publishedYes

Fingerprint

p21-Activated Kinases
Calmodulin-Binding Proteins
Protein Kinases
Smooth Muscle
Calcium
Phosphorylation
Glutathione Transferase
Canidae
Desmin
Protein Isoforms
Swine
Western Blotting
Antibodies

Keywords

  • Asthma
  • Calcium sensitization
  • Monomeric G proteins
  • p21-activated kinase
  • Tonic smooth muscle

ASJC Scopus subject areas

  • Pulmonary and Respiratory Medicine
  • Cell Biology
  • Physiology

Cite this

Calcium-independent contraction and sensitization of airway smooth muscle by p21-activated protein kinase. / McFawn, P. K.; Shen, L.; Vincent, S. G.; Mak, A.; Van Eyk, J. E.; Fisher, J. T.

In: American Journal of Physiology - Lung Cellular and Molecular Physiology, Vol. 284, No. 5 28-5, 01.05.2003.

Research output: Contribution to journalArticle

McFawn, P. K. ; Shen, L. ; Vincent, S. G. ; Mak, A. ; Van Eyk, J. E. ; Fisher, J. T. / Calcium-independent contraction and sensitization of airway smooth muscle by p21-activated protein kinase. In: American Journal of Physiology - Lung Cellular and Molecular Physiology. 2003 ; Vol. 284, No. 5 28-5.
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AU - McFawn, P. K.

AU - Shen, L.

AU - Vincent, S. G.

AU - Mak, A.

AU - Van Eyk, J. E.

AU - Fisher, J. T.

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AB - In Triton-skinned phasic ileal smooth muscle, constitutively active recombinant p21-activated kinase (PAK3) has been shown to induce Ca2+-independent contraction, which is accompanied by phosphorylation of caldesmon and desmin (Van Eyk JE, Arrell DK, Foster DB, Strauss JD, Heinonen TY, Furmaniak-Kazmierczak E, Cote GP, and Mak AS. J Biol Chem 273: 23433-23439, 1998). In the present study, we investigated whether PAK has a broad impact on smooth muscle in general by testing the hypothesis that PAK induces Ca2+-independent contractions and/or Ca2+ sensitization in tonic airway smooth muscle and that the process is mediated via phosphorylation of caldesmon. In the absence of Ca2+ (pCa > 9), constitutively active glutathione-S-transferase-murine PAK3 (GST-mPAK3) caused force generation of Triton-skinned canine tracheal smooth muscle (TSM) fibers to ∼40% of the maximal force generated by Ca2+ at pCa 4.4. In addition, GST-mPAK3 enhanced Ca2+ sensitivity of contraction by increasing force generation by 80% at intermediate Ca2+ concentrations (pCa 6.2), whereas it had no effect at pCa 4.4. Catalytically inactive GST-mPAK3K297R had no effect on force production. Using antibody against one of the PAK-phosphorylated sites (Ser657) on caldesmon, we showed that a basal level of phosphorylation of caldesmon occurs at this site in skinned TSM and that PAK-induced contraction was accompanied by a significant increase in the level of phosphorylation. Western blot analyses show that PAK1 is the predominant PAK isoform expressed in murine, rat, canine, and porcine TSM. We conclude that PAK causes Ca2+-independent contractions and produces Ca2+ sensitization of skinned phasic and tonic smooth muscle, which involves an incremental increase in caldesmon phosphorylation.

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