Caveolae facilitate muscarinic receptor-mediated intracellular Ca2+ mobilization and contraction in airway smooth muscle

doi:10.1152/ajplung.00312.2007

Caveolae facilitate muscarinic receptor-mediated intracellular Ca²⁺ mobilization and contraction in airway smooth muscle

Reinoud Gosens,¹^,2^,3^,4^,5^,* Gerald L. Stelmack,¹^,2^,3^,* Gordon Dueck,¹^,3^,4 Mark M. Mutawe,¹^,2^,3 Martha Hinton,¹^,3^,6 Karol D. McNeill,¹^,2 Angela Paulson,¹^,3^,4 Shyamala Dakshinamurti,¹^,6 William T. Gerthoffer,⁷ James A. Thliveris,⁸ Helmut Unruh,⁹ Johan Zaagsma,⁵ and Andrew J. Halayko¹^,2^,3^,4^,6

Departments of ¹Physiology, ²Internal Medicine, ⁶Pediatrics and Child Health, and ⁸Human Anatomy and Cell Science, University of Manitoba, ³Biology of Breathing Group, Manitoba Institute of Child Health, ⁴Canadian Institutes of Health Research National Training Program in Allergy and Asthma, University of Manitoba, and ⁹Section of Thoracic Surgery, University of Manitoba, Winnipeg, Manitoba, Canada; ⁵Department of Molecular Pharmacology, University of Groningen, Groningen, The Netherlands; and ⁷Department of Pharmacology, University of Nevada School of Medicine, Reno, Nevada

Submitted 4 August 2007 ; accepted in final form 20 September 2007

Contractile responses of airway smooth muscle (ASM) determineairway resistance in health and disease. Caveolae microdomainsin the plasma membrane are marked by caveolin proteins and areabundant in contractile smooth muscle in association with nanospacesinvolved in Ca²⁺ homeostasis. Caveolin-1 can modulate localizationand activity of signaling proteins, including trimeric G proteins,via a scaffolding domain. We investigated the role of caveolaein contraction and intracellular Ca²⁺ ([Ca²⁺]_i) mobilizationof ASM induced by the physiological muscarinic receptor agonist,acetylcholine (ACh). Human and canine ASM tissues and cellspredominantly express caveolin-1. Muscarinic M₃ receptors (M₃R)and G ${alpha}$ _q/11 cofractionate with caveolin-1-rich membranes of ASMtissue. Caveolae disruption with β-cyclodextrin in caninetracheal strips reduced sensitivity but not maximum isometricforce induced by ACh. In fura-2-loaded canine and human ASMcells, exposure to methyl-β-cyclodextrin (mβCD) reducedsensitivity but not maximum [Ca²⁺]_i induced by ACh. In contrast,both parameters were reduced for the partial muscarinic agonist,pilocarpine. Fluorescence microscopy revealed that mβCDdisrupted the colocalization of caveolae-1 and M₃R, but [N-methyl-³H]scopolaminereceptor-binding assay revealed no effect on muscarinic receptoravailability or affinity. To dissect the role of caveolin-1in ACh-induced [Ca²⁺]_i flux, we disrupted its binding to signalingproteins using either a cell-permeable caveolin-1 scaffoldingdomain peptide mimetic or by small interfering RNA knockdown.Similar to the effects of mβCD, direct targeting of caveolin-1reduced sensitivity to ACh, but maximum [Ca²⁺]_i mobilizationwas unaffected. These results indicate caveolae and caveolin-1facilitate [Ca²⁺]_i mobilization leading to ASM contraction inducedby submaximal concentrations of ACh.

caveolin; G protein-coupled receptor; asthma; histamine; G ${alpha}$ _q

Address for reprint requests and other correspondence: A. J. Halayko, Dept. of Physiology, Univ. of Manitoba, 715 McDermot Ave., Rm. 547, John Buhler Research Centre, Winnipeg, Manitoba, Canada, R3E 3P4 (e-mail: ahalayk{at}cc.umanitoba.ca)

This article has been cited by other articles:

P. Sharma, T. Tran, G. L. Stelmack, K. McNeill, R. Gosens, M. M. Mutawe, H. Unruh, W. T. Gerthoffer, and A. J. Halayko
Expression of the dystrophin-glycoprotein complex is a marker for human airway smooth muscle phenotype maturation
Am J Physiol Lung Cell Mol Physiol, January 1, 2008; 294(1): L57 - L68.
[Abstract] [Full Text] [PDF]