Laminin acts via β1 integrin signalling to alter cholinergic regulation of L‐type Ca2+ current in cat atrial myocytes

Open Access
Publisher Website
Google Scholar
Abstract
1 A perforated patch recording method was used to determine how plating cells on laminin (20 μg ml−1; >2 h) alters cholinergic regulation of L-type Ca2+ current (ICa,L) in atrial myocytes. 2 Acetylcholine (ACh; 1 μm)-induced inhibition of basal ICa,L was not different between cells on glass and laminin. However, stimulation of ICa,L elicited by ACh withdrawal was significantly smaller in cells on laminin (10 ± 2 %) than on glass (48 ± 5 %) (P= 0.001). 3 Stimulation of ICa,L induced by either spermine-NO (200 μm), milrinone (10 μm), IBMX (100 μm) or forskolin (1 μm) was significantly smaller in cells plated on laminin than on glass. However, stimulation of ICa,L by 100 μm 8-CPT-cAMP or intracellular dialysis with 50 μM cAMP was not different between cells plated on laminin or glass. 4 Basal, forskolin- and IBMX-stimulated cAMP content was significantly smaller in cells plated on laminin than on glass. 5 Stimulation of ICa,L by ACh withdrawal was significantly smaller in cells plated on an αβ1-integrin antibody (10 ± 4 %) than on glass (38 ± 6 %; P= 0.001). In cells on laminin, prior exposure to 100 μg ml−1 YIGSR, a laminin receptor-binding peptide, restored ACh-induced stimulation of ICa,L (58 ± 14 %)laminin alone (7 ± 2 %; P= 0.05). 6 Addition of 20 μm cytochalasin D or 1 μM latrunculin A, agents that prevent actin polymerization, to cells on laminin restored ACh-induced stimulation of ICa,L. 7 We conclude that laminin binding to β1 integrins acts in association with the actin-based cytoskeleton to attenuate adenylate cyclase activity. As a result, laminin inhibits NO-mediated stimulation of ICa,L elicited by ACh withdrawal. Laminin-integrin signalling may be relevant to changes in autonomic regulation that occur during cardiac development and/or disease.