Aluminum fluoride inhibits phospholipase D activation by a GTP-binding protein-independent mechanism

Aluminum fluoride (AlF4-;) inhibited guanine nucleotide-activated phospholi pase D (PLD) in rat submandibular gland cell-free lysates in a concentratio n-dependent response. This effect was consistent in permeabilized cells wit h endogenous phospholipid PLD substrates, Inhibition was not caused by eith er fluoride or aluminum alone and was reversed by aluminum chelation, Inhib ition of PLD by aluminum fluoride was not mediated by cAMP, phosphatases 1, 2A or 2B, or phosphatidate phosphohydrolase. AlF4- had a similar inhibitor y effect on rArf-stimulated PLD, but did not block the translocation of Arf from cytosol to membranes, indicating a post-GTP-binding-protein site of a ction. Oleate-sensitive PLD, which is not guanine nucleotide-dependent, was also inhibited by AlF4-;, supporting a G protein-independent mechanism of action, A submandibular Golgi-enriched membrane preparation had high PLD ac tivity which was also potently inhibited by AlF4-;, leading to speculation that the known fluoride inhibition of Golgi vesicle transport may be PLD-me diated. It is proposed that aluminum fluoride inhibits different forms of P LD by a mechanism that is independent of GTP-binding proteins and that acts via a membrane-associated target which may be the enzyme itself (C) 1999 F ederation of European Biochemical Societies.