title: Regulation of phospholipase C-delta1 through direct interactions with the small GTPase Ral and calmodulin.
abstract: Second messengers generated from membrane lipids play a critical role in signaling and control diverse cellular processes. Despite being one of the most evolutionarily conserved of all the phosphoinositide-specific phospholipase C (PLC) isoforms, a family of enzymes responsible for hydrolysis of the membrane lipid phosphatidylinositol bisphosphate, the mechanism of PLC-delta1 activation is still poorly understood. Here we report a novel regulatory mechanism for PLC-delta1 activation that involves direct interaction of the small GTPase Ral and the universal calcium-signaling molecule calmodulin (CaM) with PLC-delta1. In addition, we have identified a novel IQ type CaM binding motif within the catalytic region of PLC-delta1 that is not found in other PLC isoforms. Binding of CaM at the IQ motif inhibits PLC-delta1 activity, while addition of Ral reverses the inhibition. The overexpression of various Ral mutants in cells potentiates PLC-delta1 activity. Thus, the Ral-CaM complex defines a multifaceted regulatory mechanism for PLC-delta1 activation.
authors.affiliation: Department of Oral Biology, Faculty of Dentistry, University of Manitoba, Winnipeg, Manitoba R3E 0W2, Canada.
authors.forename: Ranjinder S
authors.initials: RS
authors.lastname: Sidhu
authors.forename: Richard R
authors.initials: RR
authors.lastname: Clough
authors.forename: Rajinder P
authors.initials: RP
authors.lastname: Bhullar
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D002147:Calmodulin / Q000737:chemistry*; D002384:Catalysis; D020134:Catalytic Domain; D002417:Cattle; D002462:Cell Membrane / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism; D020558:GTP Phosphohydrolases / Q000737:chemistry*; D015723:Gene Library; D005982:Glutathione Transferase / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D006868:Hydrolysis; D007527:Isoenzymes / Q000235:genetics / Q000502:physiology*; D008958:Models, Molecular; D009154:Mutation; D010455:Peptides / Q000737:chemistry; D010710:Phosphates / Q000737:chemistry; D010716:Phosphatidylinositols / Q000737:chemistry; D054803:Phospholipase C delta; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry; D015398:Signal Transduction; D013696:Temperature; D014162:Transfection; D020798:Two-Hybrid System Techniques; D010738:Type C Phospholipases / Q000235:genetics / Q000502:physiology*; D020725:ral GTP-Binding Proteins / Q000378:metabolism*
chemical_list: D002147:Calmodulin; D018076:DNA, Complementary; D007527:Isoenzymes; D010455:Peptides; D010710:Phosphates; D010716:Phosphatidylinositols; D020033:Protein Isoforms; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D005982:Glutathione Transferase; D010738:Type C Phospholipases; C518024:PLCD1 protein, human; D054803:Phospholipase C delta; C518026:Plcd1 protein, rat; D020558:GTP Phosphohydrolases; D020725:ral GTP-Binding Proteins; D002118:Calcium