title: Calcium receptor stimulates chemotaxis and secretion of MCP-1 in GnRH neurons in vitro: potential impact on reduced GnRH neuron population in CaR-null mice.
abstract: The factors controlling the migration of mammalian gonadotropin-releasing hormone (GnRH) neurons from the nasal placode to the hypothalamus are not well understood. We studied whether the extracellular calcium-sensing receptor (CaR) promotes migration/chemotaxis of GnRH neurons. We demonstrated expression of CaR in GnRH neurons in the murine basal forebrain and in two GnRH neuronal cell lines: GT1-7 (hypothalamus derived) and GN11 (olfactory bulb derived). Elevated extracellular Ca(2+) concentrations promoted chemotaxis of both cell types, with a greater effect in GN11 cells. This effect was CaR mediated, as, in both cell types, overexpression of a dominant-negative CaR attenuated high Ca(2+)-stimulated chemotaxis. We also demonstrated expression of a beta-chemokine, monocyte chemoattractant protein-1 (MCP-1), and its receptor, CC motif receptor-2 (CCR2), in the hypothalamic GnRH neurons as well as in GT1-7 and GN11 cells. Exogenous MCP-1 stimulated chemotaxis of both cell lines in a dose-dependent fashion; the effect was greater in GN11 than in GT1-7 cells, consistent with the higher CCR2 mRNA levels in GN11 cells. Activating the CaR stimulated MCP-1 secretion in GT1-7 but not in GN11 cells. MCP-1 secreted in response to CaR stimulation is biologically active, as conditioned medium from GT1-7 cells treated with high Ca(2+) promoted chemotaxis of GN11 cells, and this effect was partially attenuated by a neutralizing antibody to MCP-1. Finally, in the preoptic area of anterior hypothalamus, the number of GnRH neurons was approximately 27% lower in CaR-null mice than in mice expressing the CaR gene. We conclude that the CaR may be a novel regulator of GnRH neuronal migration likely involving, in part, MCP-1.
authors.affiliation: Division of Endocrinology, Diabetes and Hypertension, Department of Medicine and Membrane Biology Program, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA. Naibedya@cdriindia.org
authors.forename: Naibedya
authors.initials: N
authors.lastname: Chattopadhyay
authors.forename: Kyeong-Hoon
authors.initials: KH
authors.lastname: Jeong
authors.forename: Shozo
authors.initials: S
authors.lastname: Yano
authors.forename: Su
authors.initials: S
authors.lastname: Huang
authors.forename: Jian L
authors.initials: JL
authors.lastname: Pang
authors.forename: Xianghui
authors.initials: X
authors.lastname: Ren
authors.forename: Ernest
authors.initials: E
authors.lastname: Terwilliger
authors.forename: Ursula B
authors.initials: UB
authors.lastname: Kaiser
authors.forename: Peter M
authors.initials: PM
authors.lastname: Vassilev
authors.forename: Martin R
authors.initials: MR
authors.lastname: Pollak
authors.forename: Edward M
authors.initials: EM
authors.lastname: Brown
mesh_terms: D000818:Animals; D002118:Calcium / Q000502:physiology; D002452:Cell Count; D002478:Cells, Cultured; D018932:Chemokine CCL2 / Q000378:metabolism*; D002633:Chemotaxis; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D009474:Neurons / Q000166:cytology* / Q000378:metabolism*; D054390:Receptors, CCR2; D044169:Receptors, Calcium-Sensing / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D019707:Receptors, Chemokine / Q000378:metabolism
chemical_list: C491768:Ccl2 protein, mouse; C515335:Ccr2 protein, mouse; D018932:Chemokine CCL2; D054390:Receptors, CCR2; D044169:Receptors, Calcium-Sensing; D019707:Receptors, Chemokine; D007987:Gonadotropin-Releasing Hormone; D002118:Calcium