We examined the function of the pimA (Rv2610c) gene, located in the vicinity of the phosphatidylinositol synthase gene in the genomes of Mycobacterium tuberculosis and Mycobacterium smegmatis, which encodes a putative mannosyltransferase involved in the early steps of phosphatidylinositol mannoside synthesis. A cell-free assay was developed in which membranes from M. smegmatis overexpressing th...

The addition of the Ca2+ ionophore A23187 to rabbit neutrophils stimulated [14C]arachidonic acid incorporation into phosphatidylinositol and lysosomal enzyme secretion. A significant increase in phosphatidylinositol labelling was observed after a 2 min exposure to 0.1 microM-ionophore A23187. Maximum increases in rate of labelling were obtained with 1 microM-ionophore A23187 within 1 min, decli...

We have screened toyocamycin as an inhibitor of phosphatidylinositol kinase. It inhibited the enzyme of A431 cell membrane with an IC50 of 3.3 micrograms/ml. Adenosine and formycin A also inhibited the enzyme, but other 6 related nucleosides did not. Although orobol and 2,3-dihydroxybenzaldehyde that inhibit phosphatidylinositol kinase inhibited in situ phosphatidylinositol turnover, toyocamyci...

The hydrolysis of membrane-bound phosphatidylinositol in rat liver microsomal fraction by the soluble phosphatidylinositol phosphodiesterase from rat brain was markedly stimulated by oleic acid or arachidonic acid. The stimulation did not require added calcium, although it was abolished by EDTA. Lysophosphatidylcholine also totally suppressed the stimulation. A possible role for the fatty acid ...

Rho and Rac small GTPases associate with type-I phosphatidylinositol 4-phosphate 5-kinase to regulate the production of phosphatidylinositol 4,5-bisphosphate. This lipid appears to mediate some of the effects of Rho and Rac on the actin cytoskeleton. The genes for several type-I phosphatidylinositol 4-phosphate 5-kinases have been cloned recently but it is not known which one interacts with Rho...

PTEN/MMAC1 is a tumor suppressor gene that is mutated in a variety of cancers. PTEN encodes a phosphatase that recognizes phosphoprotein substrates and the phospholipid, phosphatidylinositol-3,4,5-triphosphate. PTEN inhibited cell growth and/or colony formation in all of the epithelial lines tested with one exception. The decrease in cellular proliferation was associated with an induction of ap...

A number of drugs classed as calcium antagonists, spasmolytics, non-specific receptor antagonists or receptor antagonists with multiple sites of action were tested to determine whether they prevent the stimulation of phosphatidylinositol turnover caused in various tissues by the activation of receptors which increase cell-surface Ca2+ permeability. The experiments were done with fragments of lo...