Serum-induced membrane depolarization in quiescent fibroblasts: activation of a chloride conductance through the G protein-coupled LPA receptor.
Serum stimulation of quiescent fibroblasts leads to a dramatic depolarization of the plasma membrane; however, the identity of the active serum factor(s) and the underlying mechanism are unknown. We find that this serum activity is attributable to albumin-bound lysophosphatidic acid (LPA) acting on its own G protein-coupled receptor, and that membrane depolarization is due to activation of an anion conductance mediating Cl- efflux. This depolarizing Cl- current can also be activated by thrombin and neuropeptide receptors; it is distinct from volume-regulated Cl- currents. Activation of the Cl- current consistently follows stimulation of phospholipase C and coincides with remodelling of the actin cytoskeleton, which is regulated by the Ras-related GTPase Rho. However, the response is not due to Ca2+/protein kinase C signalling and requires neither Rho nor Ras activation. The results indicate that in quiescent fibroblasts, LPA and other G protein-coupled receptor agonists evoke membrane depolarization by activating a new type of Cl- channel through a signalling pathway that is closely associated with phosphoinositide hydrolysis, yet independent of known second messengers.
Postma
F R
FR
Division of Cellular Biochemistry, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam.
Jalink
K
K
Hengeveld
T
T
Bot
A G
AG
Alblas
J
J
de Jonge
H R
HR
Moolenaar
W H
WH
D000818:Animals; D048429:Cell Size; D002478:Cells, Cultured; D018118:Chloride Channels / Q000502:physiology*; D002712:Chlorides / Q000502:physiology; D005347:Fibroblasts; D019204:GTP-Binding Proteins / Q000378:metabolism / Q000502:physiology; D015640:Ion Channel Gating; D008564:Membrane Potentials; D051381:Rats; D011956:Receptors, Cell Surface / Q000502:physiology*; D043562:Receptors, G-Protein-Coupled; D049368:Receptors, Lysophosphatidic Acid; D012709:Serum Albumin / Q000502:physiology*; D010738:Type C Phospholipases / Q000502:physiology; D020741:rho GTP-Binding Proteins
D018118:Chloride Channels; D002712:Chlorides; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D049368:Receptors, Lysophosphatidic Acid; D012709:Serum Albumin; D010738:Type C Phospholipases; D019204:GTP-Binding Proteins; D020741:rho GTP-Binding Proteins