Laminin enhances β2-adrenergic receptor stimulation of L-type Ca2+ current via cytosolic phospholipase A2 signalling in cat atrial myocytes

We previously reported that attachment of atrial myocytes to the extracellular matrix protein laminin (LMN), decreases adenylate cyclase (AC)/cAMP and increases β 2 -adrenergic receptor (AR) stimulation of L-type Ca 2+ current ( I Ca,L ). This study therefore sought to determine whether LMN enhance...

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Veröffentlicht in:The Journal of physiology 2009-10, Vol.587 (20), p.4785
Hauptverfasser: M. R. Pabbidi, X. Ji, A. M. Samarel, S. L. Lipsius
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Sprache:eng
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Zusammenfassung:We previously reported that attachment of atrial myocytes to the extracellular matrix protein laminin (LMN), decreases adenylate cyclase (AC)/cAMP and increases β 2 -adrenergic receptor (AR) stimulation of L-type Ca 2+ current ( I Ca,L ). This study therefore sought to determine whether LMN enhances β 2 -AR signalling via a cAMP-independent mechanism, i.e. cytosolic phospholipase A 2 (cPLA 2 ) signalling. Studies were performed on acutely isolated atrial myocytes plated on uncoated coverslips (−LMN) or coverslips coated with LMN (+LMN). As previously reported, 0.1 μ m zinterol (zint-β 2 -AR) stimulation of I Ca,L was larger in +LMN than −LMN myocytes. In +LMN myocytes, zint-β 2 -AR stimulation of I Ca,L was inhibited by inhibition of cPLA 2 by arachidonyltrifluoromethyl ketone (AACOCF 3 ; 10 μ m ), inhibition of G i by pertussis toxin and chelation of intracellular Ca 2+ by 10 μ m BAPTA-AM. In contrast to zinterol, stimulation of I Ca,L by fenoterol (fen-β 2 -AR), a β 2 -AR agonist that acts exclusively via G s signalling, was smaller in +LMN than −LMN myocytes. Arachidonic acid (AA; 5 μ m ) stimulated I Ca,L to a similar extent in −LMN and +LMN myocytes. Inhibition of cAMP-dependent protein kinase A (cAMP/PKA) by either 5 μ m H−89 or 1 μ m KT5720 in −LMN myocytes mimicked the effects of +LMN myocytes to enhance zint-β 2 -AR stimulation of I Ca,L , which was blocked by 10 μ m AACOCF 3 . In contrast, H−89 inhibited fen-β 2 -AR stimulation of I Ca,L , which was unchanged by AACOCF 3 . Inhibition of ERK1/2 by 1 μ m U0126 inhibited zint-β 2 -AR stimulation of I Ca,L in +LMN myocytes and −LMN myocytes in which cAMP/PKA was inhibited by KT5720. In −LMN myocytes, cytochalasin D prevented inhibition of cAMP/PKA from enhancing zint-β 2 -AR stimulation of I Ca,L . We conclude that LMN enhances zint-β 2 -AR stimulation of I Ca,L via G i /ERK1/2/cPLA 2 /AA signalling which is activated by concomitant inhibition of cAMP/PKA signalling and dependent on the actin cytoskeleton. These findings provide new insight into the cellular mechanisms by which the extracellular matrix can remodel β 2 -AR signalling in atrial muscle.
ISSN:0022-3751
1469-7793
DOI:10.1113/jphysiol.2009.179226