Activation of certain phosphoinositidase-C-linked cell-surface receptors is known to cause an acceleration of the proteolysis of inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] receptors and, thus, lead to Ins(1,4,5)P3-receptor down-regulation. In the current study we have sought to determine whether the ubiquitin/proteasome pathway is involved in this adaptive response. The data presented show (i)...

Mycobacteria and other actinomycetes do not produce glutathione but make mycothiol (MSH; AcCys-GlcN-Ins) that has functions similar to those of glutathione and is essential for growth of Mycobacterium tuberculosis. Mycothiol synthase (MshD) catalyzes N acetylation of Cys-GlcN-Ins to produce MSH in Mycobacterium smegmatis mc2155, and Cys-GlcN-Ins is maintained at a low level. The mycothiol synth...

The metabolism of inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] was examined in yeast cells and germ tubes of Candida albicans. Methods have been developed for analysis of the two key metabolic enzymes, Ins(1,4,5)P3, kinase and phosphatase. ATP-dependent Ins(1,4,5)P3 kinase activity was detected predominantly in the soluble fraction of cell extracts and exhibited a Km of approximately 9 microM. T...

The interaction of the only reported plant inositol trisphosphate receptor with different myo-inositol trisphosphates (InsP3 species), namely Ins(1,4,5)P3, Ins(1,3,4)P3, Ins(1,5,6)P3, and Ins(2,4,5)P3, were studied to assess the extent of Ca2+ mobilization from microsomes/vacuoles as well as liposomes in vitro. Ins(1,4,5)P3 and Ins(2,4,5)P3 bind with the receptor with comparable affinities, as ...

Inositol (1,4,5)-trisphosphate [Ins(1,4,5)P(3)] originating in the vascular smooth-muscle cells (VSMCs) has been shown to modulate the Ca(2+) stores in endothelial cells (ECs). However, the reverse is not found, suggesting that Ins(1,4,5)P(3) movement might be unidirectional across gap junctions at the myoendothelial junction (MEJ), or that distribution of the Ins(1,4,5)P(3) receptor [Ins(1,4,5...

An assay is described which allows the determination of the mass of any individual inositol phosphate (InsP) isomer by combining a popular h.p.l.c. separation method with simple desalting, dephosphorylation and final measurement of Ins liberated using an inositol dehydrogenase-NADH-linked bioluminescence reaction. The limit of sensitivity of this assay is about 1 pmol of Ins. routinely 5 pmol. ...

The phosphatidylinositol (PI) hydrolysis signaling system has been shown to be altered in platelets of depressed and schizophrenic subjects. Inositol (1,4,5) trisphosphate (Ins(1,4,5)P(3)), an integral component of the PI signaling system, mobilizes Ca(2+) by activating Ins(1,4,5)P(3) receptors. To eventually investigate the role of Ins(1,4,5)P(3) receptors in depression and other mental disord...

We studied the dephosphorylation pathway for Ins(1,3,4)P3 (inositol 1,3,4-trisphosphate) by liver homogenates and soluble and particulate subfractions incubated in media resembling physiological ionic strength and pH. Ins(1,3,4)P3 was dephosphorylated to two InsP2 (inositol bisphosphate) isomers, one of which is Ins(3,4)P2 [Shears, Parry, Tang, Irvine, Michell & Kirk (1987) Biochem. J. 246, 139...