The affinities of human platelet and Acanthamoeba profilin isoforms for polyphosphoinositides account for their relative abilities to inhibit phospholipase C.

L. M. Machesky, Pascal Goldschmidt-Clermont, T. D. Pollard

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Abstract

In light of recent work implicating profilin from human platelets as a possible regulator of both cytoskeletal dynamics and inositol phospholipid-mediated signaling, we have further characterized the interaction of platelet profilin and the two isoforms of Acanthamoeba profilin with inositol phospholipids. Profilin from human platelets binds to phosphatidylinositol-4-monophosphate (PIP) and phosphatidylinositol-4,5-bisphosphate (PIP2) with relatively high affinity (Kd approximately 1 microM for PIP2 by equilibrium gel filtration), but interacts only weakly (if at all) with phosphatidylinositol (PI) or inositol trisphosphate IP3) in small-zone gel-filtration assays. The two isoforms of Acanthamoeba profilin both have a lower affinity for PIP2 than does human platelet profilin, but the more basic profilin isoform from Acanthamoeba (profilin-II) has a much higher (approximately 10-microM Kd) affinity than the acidic isoform (profilin-I, 100 to 500-microM Kd). None of the profilins bind to phosphatidylserine (PS) or phosphatidylcholine (PC) in small-zone gel-filtration experiments. The differences in affinity for PIP2 parallel the ability of these three profilins to inhibit PIP2 hydrolysis by soluble phospholipase C (PLC). The results show that the interaction of profilins with PIP2 is specific with respect to both the lipid and the proteins. In Acanthamoeba, the two isoforms of profilin may have specialized functions on the basis of their identical (approximately 10 microM) affinities for actin monomers and different affinities for PIP2.

Original languageEnglish
Pages (from-to)937-950
Number of pages14
JournalCell regulation
Volume1
Issue number12
StatePublished - Nov 1 1990
Externally publishedYes

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Profilins
Acanthamoeba
Phosphatidylinositol Phosphates
Type C Phospholipases
Protein Isoforms
Blood Platelets
Phosphatidylinositols
Gel Chromatography
Phosphatidylserines
Inositol
Phosphatidylcholines

ASJC Scopus subject areas

  • Medicine(all)

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The affinities of human platelet and Acanthamoeba profilin isoforms for polyphosphoinositides account for their relative abilities to inhibit phospholipase C. / Machesky, L. M.; Goldschmidt-Clermont, Pascal; Pollard, T. D.

In: Cell regulation, Vol. 1, No. 12, 01.11.1990, p. 937-950.

Research output: Contribution to journalArticle

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