High impact information on IPK1

• These data confirm the involvement of IPK2 and IPK1 in the conversion of inositol 1,4,5-trisphosphate to IP6 in rat cells [1].
• Production of inositol hexakisphosphate (IP6) by Ipk1, the inositol-1,3,4,5,6-pentakisphosphate 2-kinase, is required for Gle1-mediated mRNA export in Saccharomyces cerevisiae cells [2].
• Moreover, coincident sequestering of both Ipk1 and Mss4 (an enzyme required for phosphatidylinositol 4,5-bisphosphate production) to the cytoplasm also did not block IP6 production [2].
• The synthesis of inositol hexakisphosphate. Characterization of human inositol 1,3,4,5,6-pentakisphosphate 2-kinase [3].
• In fungal cells, a 2-kinase designated Ipk1 is responsible for synthesis of InsP(6) by phosphorylation of inositol 1,3,4,5,6-pentakisphosphate (InsP(5)) [3].

Biological context of IPK1

• In budding yeast, IP(6) synthesis occurs through the sequential phosphorylation of I(1,4,5)P(3) by two gene products, Ipk2 and Ipk1, a IP(3)/IP(4) dual-specificity 6-/3-kinase and an inositol 1,3,4,5,6-pentakisphosphate 2-kinase, respectively [4].
• Both of these phenotypes are complemented by expression of the spIPK1 gene in the sc-ipk1 cells [5].
• PtdIns(4,5)P2 hydrolysis occurs normally in mutants lacking Arg82p or Ipk1p, but they accumulate no InsP6, showing that these enzymes normally convert the liberated Ins(1,4,5)P3 rapidly and quantitatively to InsP6 [6].
• Based on limited conserved sequence motifs among five Ipk1 proteins from different fungal species, we have identified a human genomic DNA sequence on chromosome 9 that encodes human inositol 1,3,4,5,6-pentakisphosphate 2-kinase (InsP(5) 2-kinase) [3].
• Like S. cerevisiae Gsc/Fks proteins, none of the predicted products of C. albicans GSC1, GSL1, or GSL2 displayed obvious signal sequences at their N-terminal ends, but each product possessed 10 to 16 potential transmembrane helices with a relatively long cytoplasmic domain in the middle of the protein [7].

Associations of IPK1 with chemical compounds

• IP(3) accumulation upon glucose addition was completely absent in the plc1Delta strain and was amplified both by deletion of either ARG82 or IPK1 genes and by overexpression of PLC1 [8].
• The ability to modulate the intracellular inositol polyphosphate levels by altering IPK2 and IPK1 expression in rat cells will provide powerful tools to study the roles of I(1,3,4,5,6)P5 and IP6 in cell signaling [1].

Analytical, diagnostic and therapeutic context of IPK1

• Analysis of several inactive mutants and multiple sequence alignment of scIpk1, spIpk1, and a putative Candida albicans Ipk1 have identified residues involved in catalysis [5].
• Northern blotting demonstrated that C. albicans GSC1 and GSL1 but not GSL2 mRNAs were expressed in the growing yeast-phase cells [7].

References