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Neurogranin binds to phosphatidic acid and associates to cellular membranes.

ABSTRACT: Neurogranin (Ng) is a 78-amino-acid-long protein concentrated at dendritic spines of forebrain neurons that is involved in synaptic plasticity through the regulation of CaM (calmodulin)-mediated signalling. Ng features a central IQ motif that mediates binding to CaM and is phosphorylated by PKC (protein kinase C). We have analysed the subcellular distribution of Ng and found that it associates to cellular membranes in rat brain. In vitro binding assays revealed that Ng selectively binds to PA (phosphatidic acid) and that this interaction is prevented by CaM and PKC phosphorylation. Using the peptide Ng-(29-47) and a mutant with an internal deletion (Ng-IQless), we have shown that Ng binding to PA and to cellular membranes is mediated by its IQ motif. Ng expressed in NIH-3T3 cells accumulates at peripheral regions of the plasma membrane and localizes at intracellular vesicles that can be clearly visualized following saponin permeabilization. This distribution was affected by PLD (phospholipase D) and PIP5K (phosphatidylinositol 4-phosphate 5-kinase) overexpression. Based on these results, we propose that Ng binding to PA may be involved in Ng accumulation at dendritic spines and that Ng could modulate PA signalling in the postsynaptic environment.

SUBMITTER: Dominguez-Gonzalez I

PROVIDER: S-EPMC1868841 | biostudies-other | 2007 May

REPOSITORIES: biostudies-other

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Neurogranin binds to phosphatidic acid and associates to cellular membranes.

Domínguez-González Irene I Vázquez-Cuesta Silvia N SN Algaba Alicia A Díez-Guerra F Javier FJ

The Biochemical journal 20070501 1

Neurogranin (Ng) is a 78-amino-acid-long protein concentrated at dendritic spines of forebrain neurons that is involved in synaptic plasticity through the regulation of CaM (calmodulin)-mediated signalling. Ng features a central IQ motif that mediates binding to CaM and is phosphorylated by PKC (protein kinase C). We have analysed the subcellular distribution of Ng and found that it associates to cellular membranes in rat brain. In vitro binding assays revealed that Ng selectively binds to PA (p ...[more]

PMID: 17295609

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Project description:The purple sea urchin, Strongylocentrotus purpuratus, possesses a sophisticated innate immune system that functions without adaptive capabilities and responds to pathogens effectively by expressing the highly diverse SpTransformer gene family (formerly the Sp185/333 gene family). The swift gene expression response and the sequence diversity of SpTransformer cDNAs suggest that the encoded proteins have immune functions. Individual sea urchins can express up to 260 distinct SpTransformer proteins, and their diversity suggests that different versions may have different functions. Although the deduced proteins are diverse, they share an overall structure of a hydrophobic leader, a glycine-rich N-terminal region, a histidine-rich region, and a C-terminal region. Circular dichroism analysis of a recombinant SpTransformer protein, rSpTransformer-E1 (rSpTrf-E1) demonstrates that it is intrinsically disordered and transforms to α helical in the presence of buffer additives and binding targets. Although native SpTrf proteins are associated with the membranes of perinuclear vesicles in the phagocyte class of coelomocytes and are present on the surface of small phagocytes, they have no predicted transmembrane region or conserved site for glycophosphatidylinositol linkage. To determine whether native SpTrf proteins associate with phagocyte membranes through interactions with lipids, when rSpTrf-E1 is incubated with lipid-embedded nylon strips, it binds to phosphatidic acid (PA) through both the glycine-rich region and the histidine-rich region. Synthetic liposomes composed of PA and phosphatidylcholine show binding between rSpTrf-E1 and PA by fluorescence resonance energy transfer, which is associated with leakage of luminal contents suggesting changes in lipid organization and perhaps liposome lysis. Interactions with liposomes also change membrane curvature leading to liposome budding, fusion, and invagination, which is associated with PA clustering induced by rSpTrf-E1 binding. Longer incubations result in the extraction of PA from the liposomes, which form disorganized clusters. CD shows that when rSpTrf-E1 binds to PA, it changes its secondary structure from disordered to α helical. These results provide evidence for how SpTransformer proteins may associate with molecules that have exposed phosphates including PA on cell membranes and how the characteristic of protein multimerization may drive changes in the organization of membrane lipids.

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Neurogranin binds to phosphatidic acid and associates to cellular membranes.

Publications

Neurogranin binds to phosphatidic acid and associates to cellular membranes.

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