Evidence for the expression of transient receptor potential proteins in guinea pig airway smooth muscle cells

Abstract

<jats:p><jats:bold>Objective: </jats:bold> The present study investigates the expression of transient receptor potential (TRPC) proteins in airway smooth muscle (ASM) cells in order to determine whether these proteins may be candidate molecular counterparts of plasma membrane Ca<jats:sup>2+</jats:sup>‐permeable channels involved in the contraction of ASM.</jats:p><jats:p><jats:bold>Methods: </jats:bold> Expression of TRPC mRNA was detected using specific primers and RT‐PCR. Expression of the TRPC1, TRPC3 and TRPC6 proteins was detected using antibodies in immunoprecipitation and Western blot.</jats:p><jats:p><jats:bold>Results: </jats:bold> Guinea pig ASM cells exhibited thapsigargin‐ and acetylcholine‐initiated Ca<jats:sup>2+</jats:sup> inflow but none by 1‐oleoyl‐2‐acetyl<jats:italic>‐sn</jats:italic>‐glycerol. mRNA encoding each of the TRPC1 to TRPC6 proteins was detected in ASM cells. mRNA encoding TRPC1, TRPC3, TRPC4 and TRPC6 was detected in ASM cells at a concentration approximately equivalent to that in guinea pig brain. mRNA encoding TRPC2 and TRPC5 was more abundant in ASM cells than in brain. The TRPC1 protein, but not the TRPC3 or TRPC6 proteins, was detected in extracts of ASM cells, while all three proteins were detected in brain.</jats:p><jats:p><jats:bold>Conclusion: </jats:bold> The results provide evidence for a low level of expression of the TRPC1 to TRPC6 proteins in ASM cells. These proteins may function as store‐operated Ca<jats:sup>2+</jats:sup> and/or second messenger‐activated non‐selective cation channels in ASM cells.</jats:p>