Activation of a Ca2+-dependent K+ current in mouse fibroblasts by sphingosine-1-phosphate involves the protein tyrosine kinase c-Src.
Sphingosine-1-phosphate (S1P) is a phospholipid that acts through G-protein-coupled plasma membrane receptors and induces a broad spectrum of cellular responses, including proliferation, migration, differentiation and apoptosis. Here we report that in NIH3T3 and C3H10T1/2 mouse fibroblasts S1P activates a Ca2+-dependent, voltage-independent K+ current (EC50-value 113 nM) that is blocked by the K+ channel blockers charybdotoxin, margatoxin, and iberiotoxin. The K+ current activation by S1P is transient and leads to a large membrane hyperpolarization. Recently, we showed that lysophosphatidic acid (LPA), a serum lipid with similar biological effects compared to those of S1P, can activate a Ca2+-dependent K+ current in NIH3T3 cells that has identical properties compared to the one that is activated by S1P. When applied consecutively, both S1P and LPA induced a K+ current response in NIH3T3 cells, which indicates that the K+ current activation is not subjected to cross-desensitization between S1P and LPA. In C3H10T1/2 mouse fibroblasts that overexpress the nonreceptor protein tyrosine kinase c-Src, the amplitude of the S1P-induced K+ current was almost doubled compared to the one that we found in control cells. Expression of a non-myristylated c-Src mutant led to a further increase in the K+ current response to S1P, whereas expression of a kinase-defective c-Src mutant reduced it to about 40% compared to the control value. Our data show that S1P activates Ca2+-dependent K+ channels in mouse fibroblasts via an intracellular signalling pathway that involves the non-receptor protein tyrosine kinase c-Src.
Rudolf-Buchheim-Institut für Pharmakologie, Justus-Liebig-Universität Giessen, Germany.
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H
Repp
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Birringer
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Koschinski
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Dreyer
D016475:3T3 Cells / Q000187:drug effects / Q000201:enzymology / Q000502:physiology; D000818:Animals; D000081247:CSK Tyrosine-Protein Kinase; D002118:Calcium / Q000502:physiology*; D005347:Fibroblasts / Q000187:drug effects / Q000201:enzymology / Q000502:physiology; D008246:Lysophospholipids / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D051379:Mice; D008809:Mice, Inbred C3H; D009154:Mutation; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000187:drug effects* / Q000502:physiology; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D013110:Sphingosine / Q000031:analogs & derivatives / Q000494:pharmacology*; D019061:src-Family Kinases
D008246:Lysophospholipids; D026902:Potassium Channel Blockers; D015221:Potassium Channels; C060506:sphingosine 1-phosphate; D011505:Protein-Tyrosine Kinases; D000081247:CSK Tyrosine-Protein Kinase; D019061:src-Family Kinases; D013110:Sphingosine; D002118:Calcium