Synthesis and evaluation of 3-modified 1D-myo-inositols as inhibitors and substrates of phosphatidylinositol synthase and inhibitors of myo-inositol uptake by cells

1993 ◽  
Vol 36 (23) ◽  
pp. 3628-3635 ◽  
Author(s):  
Stephen C. Johnson ◽  
Jean Dahl ◽  
Tzenge Lien Shih ◽  
David J. A. Schedler ◽  
Laurens Anderson ◽  
...  
Keyword(s):  
Phosphatidylinositol Synthase ◽  
Inositol Uptake

scholarly journals The uptake of 3H-labelled monodeoxyfluoro-myo-inositols into thymocytes and their incorporation into phospholipid in permeabilized cells

1993 ◽  
Vol 291 (2) ◽  
pp. 553-560 ◽  
Author(s):  
J Offer ◽  
J C Metcalfe ◽  
G A Smith
Keyword(s):  
Cellular Responses ◽  
Effective Inhibitor ◽  
Permeabilized Cells ◽  
Label Technique ◽  
Competitive Inhibitors ◽  
Phosphatidylinositol Synthase ◽  
Potential Inhibitors ◽  
Dual Label ◽  
Inositol Uptake

Monodeoxyfluoro-myo-inositols were applied to electropermeabilized and intact thymocyte preparations to study their metabolism and uptake in order to investigate their suitability as potential inhibitors of phosphoinositide-mediated cellular responses. Only three of the monodeoxyfluoro-myo-inositols were incorporated into the phospholipids of thymocytes: 1D-3-deoxy-3-fluoro-myo-inositol, 5-deoxy-5-fluoro-myo-inositol and 1D-6-deoxy-6-fluoro-myo-inositol, all of which were weaker substrates for phosphatidylinositol synthase than was myo-inositol. The 3-, 5- and 6-fluoro analogues also behaved as competitive inhibitors, with K1 values of 350 +/- 5 microM, 350 +/- 5 microM and 2.9 +/- 2 mM respectively, compared with a Km for myo-inositol of 31 +/- 4 microM. When incubated with electropermeabilized thymocyte preparations, these three analogues of myo-inositol all formed phospholipids with chromatographic properties which corresponded to those of substituted phosphatidylinositol and phosphatidylinositol monophosphate. The uptake of myo-inositol and of the monodeoxyfluoro-myo-inositols into intact thymocytes was studied by a dual-label technique. All the monodeoxyfluoro-myo-inositols were taken up to some extent, but only 2-deoxy-2-fluoro-myo-inositol and 1D-3-deoxy-3-fluoro-myo-inositol were actively concentrated. The monodeoxyfluoro-myo-inositols were also assayed for their ability to inhibit the uptake of myo-inositol into cells. Both 2-deoxy-2-fluoro-myo-inositol and 1D-3-deoxy-3-fluoro-myo-inositol were effective inhibitors of myo-inositol uptake. Furthermore, 1D-1-deoxy-1-fluoro-myo-inositol, which was not taken up actively, was an effective inhibitor of myo-inositol uptake. The three effective inhibitors all showed Ki values of approximately 150 microM, close to the apparent Km for inositol uptake of 180 microM, and the 4-, 5- and 6-fluoro analogues had Ki values in excess of 10 mM.

Inositol Transport by Hepatopancreatic Brush-Border Membrane Vesicles of the Lobster Homarus Americanus

1988 ◽  
Vol 140 (1) ◽  
pp. 107-121
Author(s):  
TEVA SIU ◽  
GREGORY A. AHEARN
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Membrane Vesicles ◽  
Homarus Americanus ◽  
Brush Border Membrane Vesicles ◽  
Carrier Mechanism ◽  
Apparent Diffusion ◽  
Noncompetitive Inhibitor ◽  
Inositol Uptake ◽  
Glucose Carrier

The mechanism of [3H]myo-inositol transport by the lobster hepatopancreas was examined using purified brush-border membrane vesicles. Transport was stimulated by a 100 mmoll−1 inward Na+ gradient, but other cation gradients were ineffective, suggesting a Na+-dependent transfer mechanism. The transport system was most efficient at pH7.0 (both sides), rather than in the presence of a pH gradient (pHin = 7.0; pHout = 5.5) or at bilaterally low pH (pHin = pHout = 5.5). The system was shown to be electrogenic in two different ways. First, myo-inositol uptake was stimulated by anions of increasing permeability (SCN− > Cl− > gluconate). Second, an outwardly directed, valinomycin-induced K+ diffusion potential (inside negative) enhanced uptake in comparison with vesicles lacking the ionophore. Myo-inositol was transported by a carrier mechanism with an apparent Kt of 0.79mmoll−1, a Jmax of 6.3pmolmg protein−1 s−1, and by apparent diffusion with a permeability coefficient of 5.92 pmolmg protein−1s−1 (mmolT1)−1. D-Glucose was a noncompetitive inhibitor of myo-inositol uptake, but myo-inositol did not significantly reduce the transport of D-[3H]glucose. Vesicles preloaded with myo-inositol trans-stimulated [3H]myo-inositol uptake, whereas those preloaded with D-glucose did not, suggesting that the inositol carrier did not transport D-glucose. It is proposed that myo-inositol does not share the glucose carrier, and that D-glucose may modulateinositol influx by binding to a ‘regulator’ site on the inositol carrier.

scholarly journals Phosphatidylinositol synthase is required for lens structural integrity and photoreceptor cell survival in the zebrafish eye

2011 ◽  
Vol 93 (4) ◽  
pp. 460-474 ◽  
Author(s):  
Taylor R. Murphy ◽  
Thomas S. Vihtelic ◽  
Kristina E. Ile ◽  
Corey T. Watson ◽  
Gregory B. Willer ◽  
...  
Keyword(s):  
Cell Survival ◽  
Photoreceptor Cell ◽  
Structural Integrity ◽  
Phosphatidylinositol Synthase

scholarly journals Identification of Two myo-Inositol Transporter Genes of Bacillus subtilis

2002 ◽  
Vol 184 (4) ◽  
pp. 983-991 ◽  
Author(s):  
Ken-Ichi Yoshida ◽  
Yoshiyuki Yamamoto ◽  
Kaoru Omae ◽  
Mami Yamamoto ◽  
Yasutaro Fujita
Keyword(s):  
Bacillus Subtilis ◽  
Promoter Region ◽  
Genome Project ◽  
Growth Defect ◽  
Promoter Regions ◽  
Significant Similarity ◽  
Sugar Transporters ◽  
Dnase I Footprinting ◽  
Inositol Uptake

ABSTRACT Among hundreds of mutants constructed systematically by the Japanese groups participating in the functional analysis of the Bacillus subtilis genome project, we found that a mutant with inactivation of iolT (ydjK) exhibited a growth defect on myo-inositol as the sole carbon source. The putative product of iolT exhibits significant similarity with many bacterial sugar transporters in the databases. In B. subtilis, the iolABCDEFGHIJ and iolRS operons are known to be involved in inositol utilization, and its transcription is regulated by the IolR repressor and induced by inositol. Among the iol genes, iolF was predicted to encode an inositol transporter. Inactivation of iolF alone did not cause such an obvious growth defect on inositol as the iolT inactivation, while simultaneous inactivation of the two genes led to a more severe defect than the single iolT inactivation. Determination of inositol uptake by the mutants revealed that iolT inactivation almost completely abolished uptake, but uptake by IolF itself was slightly detectable. These results, as well as the Km and V max values for the IolT and IolF inositol transporters, indicated that iolT and iolF encode major and minor inositol transporters, respectively. Northern and primer extension analyses of iolT transcription revealed that the gene is monocistronically transcribed from a promoter likely recognized by ςsgr;A RNA polymerase and negatively regulated by IolR as well. The interaction between IolR and the iolT promoter region was analyzed by means of gel retardation and DNase I footprinting experiments, it being suggested that the mode of interaction is quite similar to that found for the promoter regions of the iol divergon.

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