Diversity of lysophosphatidic acid receptor-mediated intracellular calcium signaling in early cortical neurogenesis

Abstract

Lysophosphatidic acid (LPA) is a membrane-derived lysophospholipid that can induce pleomorphic effects in neural progenitor cells (NPCs) from the cerebral cortex, including alterations in ionic conductance. LPA-induced, calcium-mediated conductance changes have been reported; however, the underlying molecular mechanisms have not been determined. We show here that activation of specific cognate receptors accounts for nearly all intracellular calcium responses evoked by LPAin acutely cultured nestin-positive NPCs from the developing mouse cerebral cortex. Fast-onset changes in intracellular calcium levels required release from thapsigargin-sensitive stores by a pertussis toxin-insensitive mechanism. The influx of extracellular calcium through Cd 2+/Ni 2+-insensitive influx pathways, approximately one-half of which were Gd3+ sensitive, contributed to the temporal diversity of responses. Quantitative reverse transcription-PCR revealed the presence of all five known LPA receptors in primary NPCs, with prominent expression of LPA1 , LPA2 , and LPA4. Combined genetic and pharmacological studies indicated that NPC responses were mediated by LPA1 (∼30% of the cells), LPA2 (∼30%), a combination of receptors on single cells (∼30%), and non-LPA1,2,3 pathways (∼10%). LPA responsivity was significantly reduced in more differentiated TuJ1+ cells within cultures. Calcium transients in a large proportion of LPA-responsive NPCs were also initiated by the closely related signaling lipid S1P (sphingosine-1-phosphate). These data demonstrate for the first time the involvement of LPA receptors in mediating surprisingly diverse NPC calcium responses involving multiple receptor subtypes that function within a single cell. Compared with other known factors, lysophospholipids represent the major activator of calcium signaling identified within NPCs at this early stage in corticogenesis. Copyright©2010 the authors.