Lysophosphatidic acid signals through multiple receptors in osteoclasts to elevate cytosolic calcium concentration, evoke retraction, and promote cell survival.
Lysophosphatidic acid (LPA) is a bioactive phospholipid whose functions are mediated by multiple G protein-coupled receptors. We have shown that osteoblasts produce LPA, raising the possibility that it mediates intercellular signaling among osteoblasts and osteoclasts. Here we investigated the expression, signaling and function of LPA receptors in osteoclasts. Focal application of LPA elicited transient increases in cytosolic calcium concentration ([Ca(2+)](i)), with 50% of osteoclasts responding at approximately 400 nm LPA. LPA-induced elevation of [Ca(2+)](i) was blocked by pertussis toxin or the LPA(1/3) receptor antagonist VPC-32183. LPA caused sustained retraction of osteoclast lamellipodia and disrupted peripheral actin belts. Retraction was insensitive to VPC-32183 or pertussis toxin, indicating involvement of a distinct signaling pathway. In this regard, inhibition of Rho-associated kinase stimulated respreading after LPA-induced retraction. Real-time reverse transcription-PCR revealed transcripts encoding LPA(1) and to a lesser extent LPA(2), LPA(4), and LPA(5) receptor subtypes. LPA induced nuclear translocation of NFATc1 and enhanced osteoclast survival, effects that were blocked by VPC-32183 or by a specific peptide inhibitor of NFAT activation. LPA slightly reduced the resorptive activity of osteoclasts in vitro. Thus, LPA binds to at least two receptor subtypes on osteoclasts: LPA(1), which couples through G(i/o) to elevate [Ca(2+)](i), activate NFATc1, and promote survival, and a second receptor that likely couples through G(12/13) and Rho to evoke and maintain retraction through reorganization of the actin cytoskeleton. These findings reveal a signaling axis in bone through which LPA, produced by osteoblasts, acts on multiple receptor subtypes to induce pleiotropic effects on osteoclast activity and function.
Lapierre
Danielle M
DM
Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, The University of Western Ontario, London N6A 5C1, Ontario, Canada.
Tanabe
Natsuko
N
Pereverzev
Alexey
A
Spencer
Martha
M
Shugg
Ryan P P
RP
Dixon
S Jeffrey
SJ
Sims
Stephen M
SM
D000577:Amides / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects*; D002478:Cells, Cultured; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D008246:Lysophospholipids / Q000494:pharmacology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008954:Models, Biological; D010010:Osteoclasts / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D037342:Pertussis Toxin / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D011817:Rabbits; D051381:Rats; D049368:Receptors, Lysophosphatidic Acid / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects; D054460:rho-Associated Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
D000577:Amides; D004791:Enzyme Inhibitors; D008246:Lysophospholipids; D011725:Pyridines; D049368:Receptors, Lysophosphatidic Acid; C108830:Y 27632; D037342:Pertussis Toxin; D054460:rho-Associated Kinases; C032881:lysophosphatidic acid; D002118:Calcium