Different phospholipase-C-coupled receptors differentially regulate capacitative and non-capacitative Ca2+ entry in A7r5 cells.
Several receptors, including those for AVP (Arg8-vasopressin) and 5-HT (5-hydroxytryptamine), share an ability to stimulate PLC (phospholipase C) and so production of IP3 (inositol 1,4,5-trisphosphate) and DAG (diacylglycerol) in A7r5 vascular smooth muscle cells. Our previous analysis of the effects of AVP on Ca2+ entry [Moneer, Dyer and Taylor (2003) Biochem. J. 370, 439-448] showed that arachidonic acid released from DAG stimulated NO synthase. NO then stimulated an NCCE (non-capacitative Ca2+ entry) pathway, and, via cGMP and protein kinase G, it inhibited CCE (capacitative Ca2+ entry). This reciprocal regulation ensured that, in the presence of AVP, all Ca2+ entry occurred via NCCE to be followed by a transient activation of CCE only when AVP was removed [Moneer and Taylor (2002) Biochem. J. 362, 13-21]. We confirm that, in the presence of AVP, all Ca2+ entry occurs via NCCE, but 5-HT, despite activating PLC and evoking release of Ca2+ from intracellular stores, stimulates Ca2+ entry only via CCE. We conclude that two PLC-coupled receptors differentially regulate CCE and NCCE. We also address evidence that, in some A7r5 cells lines, AVP fails either to stimulate NCCE or inhibit CCE [Brueggemann, Markun, Barakat, Chen and Byron (2005) Biochem. J. 388, 237-244]. Quantitative PCR analysis suggests that these cells predominantly express TRPC1 (transient receptor potential canonical 1), whereas cells in which AVP reciprocally regulates CCE and NCCE express a greater variety of TRPC subtypes (TRPC1=6>2>3).
Moneer
Zahid
Z
Department of Pharmacology, University of Cambridge, Tennis Court Road, Cambridge CB2 1PD, UK.
Pino
Irene
I
Taylor
Emily J A
EJ
Broad
Lisa M
LM
Liu
Yingjie
Y
Tovey
Stephen C
SC
Staali
Leila
L
Taylor
Colin W
CW
D000818:Animals; D001127:Arginine Vasopressin / Q000502:physiology; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000502:physiology*; D020013:Calcium Signaling / Q000502:physiology*; D002460:Cell Line; D006801:Humans; D021962:Membrane Microdomains / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000502:physiology; D011956:Receptors, Cell Surface / Q000502:physiology*; D011985:Receptors, Serotonin / Q000502:physiology; D017483:Receptors, Vasopressin / Q000502:physiology; D012701:Serotonin / Q000502:physiology; D010738:Type C Phospholipases / Q000378:metabolism*
D015220:Calcium Channels; D011956:Receptors, Cell Surface; D011985:Receptors, Serotonin; D017483:Receptors, Vasopressin; D001127:Arginine Vasopressin; D012701:Serotonin; D010738:Type C Phospholipases; D002118:Calcium