title: Cytoskeletal reorganization dependence of signaling by the gonadotropin-releasing hormone receptor.
abstract: Activation of classical G protein-coupled receptors (GPCRs) like the mammalian gonadotropin-releasing hormone receptor (GnRHR) typically stimulates heterotrimeric G protein molecules that subsequently activate downstream effectors. Receptor activation of heterotrimeric G protein pathways primarily controls intermediary cell metabolism by elevation or diminution of soluble cytoplasmic second messenger molecules. We have demonstrated here that stimulation of the GnRHR also results in a dramatic change in both cell adhesion and superstructural morphology. Gonadotropin-releasing hormone (GnRH) receptor activation rapidly increases the capacity of HEK293 cells expressing the GnRHR to remain matrix-adherent in the face of fluid insults. Coinciding with this profound elevation in matrix adherence, we demonstrated a GnRH-induced alteration in both cell morphology and the de novo generation of polymerized actin structures. GnRH induction of cytoskeletal remodeling was correlated with significant increases in the tyrosine phosphorylation status of a series of cytoskeletal associated proteins, e.g. focal adhesion kinase (FAK), c-Src, and microtubule-associated protein kinase (MAPK or ERK1/2). The activation of the distal downstream effector ERK1/2 was demonstrated to be sensitive to the disrupters of cytoskeletal rearrangement, cytochalasin D and latrunculin B. In addition to the sensitivity of ERKs to cytoskeletal integrity, GnRH-induced FAK and c-Src kinase activation were sensitive to these agents and the fibronectin-integrin antagonistic RGDS peptide. Activation of ERK was dependent on its protein-protein assembly with FAK and c-Src at focal adhesion complexes. Induction of the cell remodeling event leading to this signaling complex assembly occurred primarily via GnRHR activation of the monomeric G protein Rac but not RhoA. These findings demonstrated a clear divergence of GnRHR signaling via the Rac monomeric G protein focal adhesion signaling complex assembly and cytoskeletal remodeling independent of the classical heterotrimeric G protein-controlled phospholipase C-beta pathway.
authors.affiliation: Medical Research Council Human Reproductive Sciences Unit, Edinburgh Royal Infirmary, the University of Edinburgh Chancellor's Building, 49 Little France Crescent, Edinburgh EH16 4SB, Scotland, United Kingdom.
authors.forename: Lindsay
authors.initials: L
authors.lastname: Davidson
authors.forename: Adam J
authors.initials: AJ
authors.lastname: Pawson
authors.forename: Robert P
authors.initials: RP
authors.lastname: Millar
authors.forename: Stuart
authors.initials: S
authors.lastname: Maudsley
mesh_terms: D000081247:CSK Tyrosine-Protein Kinase; D002448:Cell Adhesion; D002478:Cells, Cultured; D003599:Cytoskeleton / Q000737:chemistry / Q000502:physiology*; D004789:Enzyme Activation; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology; D006153:Guanosine Diphosphate / Q000378:metabolism; D006801:Humans; D007527:Isoenzymes / Q000502:physiology; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D054799:Phospholipase C beta; D010770:Phosphotransferases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled / Q000502:physiology; D011966:Receptors, LHRH / Q000502:physiology*; D015398:Signal Transduction; D010738:Type C Phospholipases / Q000502:physiology; D019061:src-Family Kinases
chemical_list: D007527:Isoenzymes; D011518:Proto-Oncogene Proteins; D043562:Receptors, G-Protein-Coupled; D011966:Receptors, LHRH; D006153:Guanosine Diphosphate; D007987:Gonadotropin-Releasing Hormone; D010770:Phosphotransferases; D011505:Protein-Tyrosine Kinases; D000081247:CSK Tyrosine-Protein Kinase; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496050:PTK2 protein, human; D019061:src-Family Kinases; C000631346:CSK protein, human; D020928:Mitogen-Activated Protein Kinases; D010738:Type C Phospholipases; D054799:Phospholipase C beta