Phosphatidylinositol transfer protein, cytoplasmic 1 (PITPNC1) binds and transfers Phosphatidic Acid

Abstract

Phosphatidylinositol transfer proteins (PITPs) are versatile proteins required for signal transduction and membrane traffic. The best characterised mammalian PITPs are the Class I PITPs, PITP? (PITPNA) and PITP? (PITPNB) which are single domain proteins with a hydrophobic cavity binding a phosphatidylinositol (PI) or phosphatidylcholine (PC) molecule. In this study we report the lipid binding properties of an uncharacterised soluble PITP, phosphatidylinositol transfer protein, cytoplasmic 1 (PITPNC1) (alternative name, RdgB?) of the Class II family. We show that the lipid binding properties of this protein are distinct to Class I PITPs since, beside PI, RdgB? binds and transfers phosphatidic acid (PA) but hardly PC. RdgB? when purified from E.coli is pre-loaded with PA and phosphatidylglycerol (PG) and when incubated with permeabilised HL60 cells, PG is released and PA and PI is now incorporated into RdgB?. Increasing PA levels following activation of endogenous phospholipase D or after addition of bacterial phospholipase D, binding of PA to RdgB? is increased at the expense of PI binding. We propose that RdgB?, when containing PA, regulates an effector protein or can facilitate lipid transfer between membrane compartments.

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ORCID for Alan N. Hunt: orcid.org/0000-0001-5938-2152

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