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TRPC6 is a candidate channel involved in receptor-stimulated cation currents in A7r5 smooth muscle cells
Silke Jung1, Rainer Strotmann, Günter Schultz
1Institut für Pharmakologie, Freie Universität Berlin, 14195 Berlin, Germany.
Abstract:
To investigate the possible role of members of the mammalian transient receptor potential (TRP) channel family (TRPC1-7) in vasoconstrictor-induced Ca(2+) entry in vascular smooth muscle cells, we studied [Arg(8)]-vasopressin (AVP)-activated channels in A7r5 aortic smooth muscle cells. AVP induced an increase in free cytosolic Ca(2+) concentration ([Ca(2+)](i)) consisting of Ca(2+) release and Ca(2+) influx. Whole cell recordings revealed the activation of a nonselective cation current with a doubly rectifying current-voltage relation strikingly similar to those described for some heterologously expressed TRPC isoforms. The current was also stimulated by direct activation of G proteins as well as by activation of the phospholipase Cgamma-coupled platelet-derived growth factor receptor. Currents were not activated by store depletion or increased [Ca(2+)](i). Application of 1-oleoyl-2-acetyl-sn-glycerol stimulated the current independently of protein kinase C, a characteristic property of the TRPC3/6/7 subfamily. Like TRPC6-mediated currents, cation currents in A7r5 cells were increased by flufenamate. Northern hybridization revealed mRNA coding for TRPC1 and TRPC6. We therefore suggest that TRPC6 is a molecular component of receptor-stimulated Ca(2+)-permeable cation channels in A7r5 smooth muscle cells.
Insights
This study identifies Transient Receptor Potential Canonical 6 (TRPC6) channels as key players in [Arg(8)]-vasopressin-induced calcium entry in aortic smooth muscle cells, crucial for vasoconstriction.
Area of Science:
- Physiology
- Molecular Biology
- Cardiovascular Research
Background:
- Mammalian transient receptor potential (TRP) channels are implicated in cellular signaling.
- Calcium (Ca2+) influx is vital for vascular smooth muscle cell function, including vasoconstriction.
Purpose of the Study:
- To investigate the role of TRP channels in [Arg(8)]-vasopressin (AVP)-induced Ca2+ entry in A7r5 aortic smooth muscle cells.
- To identify specific TRPC isoforms involved in receptor-stimulated cation currents.
Main Methods:
- Whole-cell patch-clamp recordings to analyze ion channel activity.
- Stimulation of cells with AVP, G protein activators, and growth factors.
- Northern hybridization to detect TRPC mRNA expression.
Main Results:
- AVP induced Ca2+ release and influx in A7r5 cells.
- A nonselective cation current, activated by AVP and G proteins, was identified.
- This current was stimulated by 1-oleoyl-2-acetyl-sn-glycerol independently of protein kinase C.
- Flufenamate enhanced the cation currents, similar to TRPC6.
- TRPC1 and TRPC6 mRNA were detected in A7r5 cells.
Conclusions:
- TRPC6 is suggested to be a molecular component of the receptor-stimulated Ca2+-permeable cation channels in vascular smooth muscle cells.
- These findings contribute to understanding the molecular mechanisms of vasoconstriction.