Inositol polyphosphates are not increased by overexpression of Ins(1,4,5)P3 3-kinase but show cell-cycle dependent changes in growth factor-stimulated fibroblasts.

Balla, Tamás; Sim, Sang Soo; Báukal, Albert J.; Rhee, Sue Goo; Catt, Kevin J.

doi:10.1091/mbc.5.1.17

Cited by 34 publications

(33 citation statements)

References 35 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Three molecular studies indicate that IP 3 3-kinases are not involved in IP 5 and IP 6 synthesis. 1) Balla et al (45) suggested that overexpression of IP 3 3-kinase did not increase higher inositol polyphosphates such as IP 5 and IP 6 in NIH 3T3 cells; 2) IP 3 3-kinase mouse knock-out cells reveal that IP 5 and IP 6 production is unaltered (46 -48); and 3) in Drosophila melanogaster loss of IP 3 3-kinase isoforms does not decrease IP 6 levels, but loss of dmIpk2 nearly ablates IP 5 and IP 6 (41).…”

Section: Discussionmentioning

confidence: 99%

A Role for Rat Inositol Polyphosphate Kinases rIPK2 and rIPK1 in Inositol Pentakisphosphate and Inositol Hexakisphosphate Production in Rat-1 Cells

Fujii

York

2005

Journal of Biological Chemistry

View full text Add to dashboard Cite

Over 30 inositol polyphosphates are known to exist in mammalian cells; however, the majority of them have uncharacterized functions. In this study we investigated the molecular basis of synthesis of highly phosphorylated inositol polyphosphates (such as inositol tetrakisphosphate, inositol pentakisphosphate (IP 5 ), and inositol hexakisphosphate (IP 6 )) in rat cells. We report that heterologous expression of rat inositol polyphosphate kinases rIPK2, a dual specificity inositol trisphosphate/inositol tetrakisphosphate kinase, and rIPK1, an IP 5 2-kinase, were sufficient to recapitulate IP 6 synthesis from inositol 1,4,5-trisphosphate in mutant yeast cells. Overexpression of rIPK2 in Rat-1 cells increased inositol 1,3,4,5,6-pentakisphosphate (I(1,3,4,5,6)P 5 ) levels about 2-3-fold compared with control. Likewise in Rat-1 cells, overexpression of rIPK1 was capable of completely converting I(1,3,4,5,6)P 5 to IP 6 . Simultaneous overexpression of both rIPK2 and rIPK1 in Rat-1 cells increased both IP 5 and IP 6 levels. To reduce IPK2 activity in Rat-1 cells, we introduced vector-based short interference RNA against rIPK2. Cells harboring the short interference RNA had a 90% reduction of mRNA levels and a 75% decrease of I(1,3,4,5,6)P 5 . These data confirm the involvement of IPK2 and IPK1 in the conversion of inositol 1,4,5-trisphosphate to IP 6 in rat cells. Furthermore these data suggest that rIPK2 and rIPK1 act as key determining steps in production of IP 5 and IP 6 , respectively. 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)P 5 and IP 6 in cell signaling.Most of the over 30 inositol polyphosphates present in mammalian cells have unknown physiological functions (1-3). One of the well characterized inositol polyphosphates is a second messenger, inositol 1,4,5-trisphosphate (I(1,4,5)P 3 ), 1 which participates in intracellular Ca 2ϩ mobilization (4) and also serves as a precursor of highly phosphorylated inositol polyphosphates such as inositol tetrakisphosphate (IP 4 ), inositol pentakisphosphate (IP 5 ), and inositol hexakisphosphate (IP 6 ) (1-3). Recently the inositol polyphosphate synthetic pathway in budding yeast, Saccharomyces cerevisiae, has been identified (5-8). In yeast, I(1,4,5)P 3 , which is hydrolyzed from phosphatidylinositol 4,5-bisphosphate by phospholipase C, is sequentially phosphorylated to IP 6 by two inositol polyphosphate kinases, a multiple specificity IP 3 /IP 4 kinase (inositol polyphosphate kinase 2 (Ipk2)) and an IP 5 2-kinase (inositol polyphosphate kinase 1 (Ipk1)). On the other hand, a synthetic pathway of IP 6 from I(1,4,5)P 3 in mammalian cells is thought to be more complex and to be a sequence of I(1,4,5)P 3 3 I(1,3,4,5)P 4 3 I(1,3,4)P 3 3 I(1,3,4,6)P 4 3 I(1,3,4,5,6)P 5 3 IP 6 (2, 3). In this pathway, IP 3 3-kinases (2), inositol polyphosphate 5-phosphatases (9), and I(1,3,4)P 3 5/6-kinase (3) appear to catalyze the first three steps to produ...

show abstract

Section: Discussionmentioning

confidence: 99%

A Role for Rat Inositol Polyphosphate Kinases rIPK2 and rIPK1 in Inositol Pentakisphosphate and Inositol Hexakisphosphate Production in Rat-1 Cells

Fujii

York

2005

Journal of Biological Chemistry

View full text Add to dashboard Cite

show abstract

“…This information, together with the new data on the kinetic parameters for Ins(1,3,4,5,6)P 5 and InsP 6 phosphorylation by mammalian type 1 InsP 6 kinase (Table II), indicates that both of these substrates will compete for phosphorylation by this enzyme in vivo. If the size of the metabolic reservoir of either substrate is modified, as happens for example during passage through the cell cycle (30,31), the metabolism of all of the diphosphorylated compounds will be affected. From this intertwined metabolism, we can further conclude that the physiological activities of all of the diphosphorylated inositol phosphates are likely to be closely linked.…”

Section: Discussionmentioning

confidence: 99%

The Inositol Hexakisphosphate Kinase Family

Saiardi¹,

Caffrey²,

Snyder³

et al. 2000

Journal of Biological Chemistry

168

123

View full text Add to dashboard Cite

Saiardi et al. (Saiardi, A., Erdjument-Bromage, H., Snowman, A., Tempst, P., and Snyder, S. H. (1999) Curr. Biol. 9, 1323-1326) previously described the cloning of a kinase from yeast and two kinases from mammals (types 1 and 2), which phosphorylate inositol hexakisphosphate (InsP 6 ) to diphosphoinositol pentakisphosphate, a "high energy" candidate regulator of cellular trafficking. We have now studied the significance of InsP 6 kinase activity in Saccharomyces cerevisiae by disrupting the kinase gene. These ip6k⌬ cells grew more slowly, their levels of diphosphoinositol polyphosphates were 60 -80% lower than wild-type cells, and the cells contained abnormally small and fragmented vacuoles. Novel activities of the mammalian and yeast InsP 6 kinases were identified; inositol pentakisphosphate (InsP 5 ) was phosphorylated to diphosphoinositol tetrakisphosphate (PP-InsP 4 ), which was further metabolized to a novel compound, tentatively identified as bisdiphosphoinositol trisphosphate. The latter is a new substrate for human diphosphoinositol polyphosphate phosphohydrolase. Kinetic parameters for the mammalian type 1 kinase indicate that InsP 5 (K m ‫؍‬ 1.2 M) and InsP 6 (K m ‫؍‬ 6.7 M) compete for phosphorylation in vivo. This is the first time a PP-InsP 4 synthase has been identified. The mammalian type 2 kinase and the yeast kinase are more specialized for the phosphorylation of InsP 6 . Synthesis of the diphosphorylated inositol phosphates is thus revealed to be more complex and interdependent than previously envisaged.The very dynamic turnover of the "high energy" diphospho- For example, PP-InsP 5 represents the most potent known inhibitor of AP180-mediated assembly of clathrin cages, a key step in the endocytic retrieval of discharged synaptosomal vesicles (2). Other proteins that participate in intracellular trafficking can bind PP-InsP 5 very tightly, including coatomer (3, 4) and AP2 (5). The high affinity with which PP-InsP 5 binds to myelin proteolipid protein may be important for the vesicular delivery of the latter to the myelin sheath (6).Prior experiments with intact cells have shown that Ins(1,3,4,5,6)P 5 and InsP 6 serve as metabolic stockpiles for the formation of the diphosphorylated inositol polyphosphates (7,8). InsP 6 is the precursor for PP-InsP 5 , which is further phosphorylated to [PP] 2 -InsP 4 (5, 7-10). These reactions appear to take place within a metabolic pool that is separate from that in which Ins(1,3,4,5,6)P 5 and PP-InsP 4 are interconverted (7). Thus, there are two metabolic pools of inositol diphosphates that are turned over in parallel cycles.There are increasing efforts to characterize the activities of the enzymes that regulate the turnover of PP-InsP 4 , PP-InsP 5 , and [PP] 2 -InsP 4 . Several phosphatases (diphosphoinositol polyphosphate phosphohydrolases) that hydrolyze these compounds have been described (11,12). Two forms of InsP 6 kinase (types 1 and 2), derived from distinct genes, have been cloned from mammals (13,14). At least in mammals, the further phosphorylati...

show abstract

“…Inositol phosphates were then resolved on two complementary high performance liquid chromatography (HPLC) systems [8,9] …”

Section: Yeast Culturing and Radiolabeling With [ 3 H]inositolmentioning

confidence: 99%

Inositol polyphosphate multikinase (ArgRIII) determines nuclear mRNA export inSaccharomyces cerevisiae

et al. 2000

View full text Add to dashboard Cite

The ARGRIII gene of Saccharomyces cerevisiae encodes a transcriptional regulator that also has inositol polyphosphate multikinase (ipmk) activity [Saiardi et al. (1999) Curr. Biol. 9, 1323^1326]. To investigate how inositol phosphates regulate gene expression, we disrupted the ARGRIII gene. This mutation impaired nuclear mRNA export, slowed cell growth, increased cellular [InsP 3 ] 170-fold and decreased [InsP 6 ] 100-fold, indicating reduced phosphorylation of InsP 3 to InsP 6 . Levels of diphosphoinositol polyphosphates were decreased much less dramatically than was InsP 6 . Low levels of InsP 6 , and considerable quantities of Ins(1,3,4,5)P 4 , were synthesized by an ipmk-independent route. Transcriptional control by ipmk reflects that it is a pivotal regulator of nuclear mRNA export via inositol phosphate metabolism.z 2000 Federation of European Biochemical Societies.

show abstract

Inositol polyphosphates are not increased by overexpression of Ins(1,4,5)P3 3-kinase but show cell-cycle dependent changes in growth factor-stimulated fibroblasts.

Cited by 34 publications

References 35 publications

A Role for Rat Inositol Polyphosphate Kinases rIPK2 and rIPK1 in Inositol Pentakisphosphate and Inositol Hexakisphosphate Production in Rat-1 Cells

A Role for Rat Inositol Polyphosphate Kinases rIPK2 and rIPK1 in Inositol Pentakisphosphate and Inositol Hexakisphosphate Production in Rat-1 Cells

The Inositol Hexakisphosphate Kinase Family

Inositol polyphosphate multikinase (ArgRIII) determines nuclear mRNA export inSaccharomyces cerevisiae

Contact Info

Product

Resources

About