title: NHERF-1 regulation of EGF and neurotensin signalling in HT-29 epithelial cells.
abstract: Neurotensin receptors (NT-R) and the epidermal growth factor receptors (EGF-R) are commonly overexpressed in many epithelial origin tumours. In addition to their role as mitogenic mediators through specific cell signalling, recent studies indicate that the activity/expression of scaffold proteins responsible for the assembly and coordination of the signalling complexes may also have central roles in epithelial transformation. In particular, the "epithelial" PSD-95/Dlg/Zo-1 (PDZ) scaffold/adapter protein, Na(+)/H(+) exchanger regulatory factor isoform one (NHERF-1), has been identified as a potential regulator of cellular transformation. NHERF-1 is a known regulator of EGF-R function and plays numerous roles in G-protein-coupled receptor signalling. Because of the synergistic signalling between these two potent mitogens, we investigated a potential role for NHERF-1 in the molecular mechanism linking the aberrant proliferative phenotype initiated by some G-Protein-coupled receptor activators in the colon adenocarcinoma HT-29 cell line. Knockdown (80%) of endogenous NHERF-1 leads to significant reduction in proliferation rate; an effect that could not be recovered by exogenous application of either NT or EGF. Inhibition of the EGF-R with AG1487 also inhibited proliferation and this effect could not be recovered with NT. Knockdown of NHERF-1 significantly altered the expression of the EGF-R, and almost completely abolished the NT-mediated increases in intracellular free Ca(2+). Knockdown of NHERF-1 also attenuated UTP-mediated purinergic Ca(2+) signalling. Taken together, these data suggest that NHERF-1 plays a more central role in cell proliferation by modulating Gq-mediated signalling pathways.
authors: Health Innovations Research Institute, School of Medical Sciences, RMIT University, Melbourne, VIC 3083, Australia.
authors: Wade A
authors: WA
authors: Kruger
authors: Gregory R
authors: GR
authors: Monteith
authors: Philip
authors: P
authors: Poronnik
mesh_terms: D020013:Calcium Signaling; D049109:Cell Proliferation; D004815:Epidermal Growth Factor / Q000378:metabolism* / Q000494:pharmacology; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism; D055785:Gene Knockdown Techniques; D019073:HT29 Cells; D006801:Humans; D009496:Neurotensin / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D010750:Phosphoproteins / Q000235:genetics / Q000502:physiology*; D043562:Receptors, G-Protein-Coupled / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000502:physiology*; D014544:Uridine Triphosphate / Q000378:metabolism
chemical_list: D010750:Phosphoproteins; D043562:Receptors, G-Protein-Coupled; D017923:Sodium-Hydrogen Exchangers; C093376:sodium-hydrogen exchanger regulatory factor; D009496:Neurotensin; D004815:Epidermal Growth Factor; C512478:EGFR protein, human; D066246:ErbB Receptors; D014544:Uridine Triphosphate