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AHNAK, a protein that binds and activates phospholipase C-gamma1 in the presence of arachidonic acid.

Authors
Sekiya, F; Bae, YS; Jhon, DY; Hwang, SC; Rhee, SG
Citation
The Journal of biological chemistry, 274(20):13900-13907, 1999
Journal Title
The Journal of biological chemistry
ISSN
0021-92581083-351X
Abstract
We have recently shown that phospholipase C-gamma (PLC-gamma) is activated by tau, a neuronal cell-specific microtubule-associated protein, in the presence of arachidonic acid. We now report that non-neuronal tissues also contain a protein that can activate PLC-gamma in the presence of arachidonic acid. Purification of this activator from bovine lung cytosol yielded several proteins with apparent molecular sizes of 70-130 kDa. They were identified as fragments derived from an unusually large protein (approximately 700 kDa) named AHNAK, which comprises about 30 repeated motifs each 128 amino acids in length. Two AHNAK fragments containing one and four of the repeated motifs, respectively, were expressed as glutathione S-transferase fusion proteins. Both recombinant proteins activated PLC-gamma1 at nanomolar concentrations in the presence of arachidonic acid, suggesting that an intact AHNAK molecule contains multiple sites for PLC-gamma activation. The role of arachidonic acid was to promote a physical interaction between AHNAK and PLC-gamma1, and the activation by AHNAK and arachidonic acid was mainly attributable to reduction in the enzyme's apparent Km toward the substrate phosphatidylinositol 4,5-bisphosphate. Our results suggest that arachidonic acid liberated by phospholipase A2 can act as an additional trigger for PLC-gamma activation, constituting an alternative mechanism that is independent of tyrosine phosphorylation.
MeSH terms
Amino Acid SequenceAnimalsArachidonic Acid/metabolism*CattleChromosomes, Human, Pair 11*Enzyme ActivationHela CellsHumansIsoenzymes/metabolism*KineticsMembrane Proteins/metabolism*Molecular Sequence DataNeoplasm Proteins/metabolism*Peptide Fragments/metabolismPhosphatidylinositol 4,5-Diphosphate/metabolismPhospholipase C gammaPhospholipases A/metabolismPhospholipases A2PhosphorylationProtein BindingType C Phospholipases/metabolism*Tyrosine/metabolismtau Proteins/metabolism
PMID
10318799
Appears in Collections:
Journal Papers > School of Medicine / Graduate School of Medicine > Medical Science
AJOU Authors
황, 성철
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