The function of inositol high polyphosphate binding proteins.
The inositol phosphate metabolism network has been found to be much more complex than previously thought, as more and more inositol phosphates and their metabolizing enzymes have been discovered. Some of the inositol phosphates have been shown to have biological activities, but little is known about their signal transduction mechanisms except for that of inositol 1,4,5-trisphosphate. The recent discovery, however, of a number of binding proteins for inositol high polyphosphate [inositol 1,3,4,5-tetrakisphosphate (IP4), inositol 1,3,4,5,6-pentakisphosphate, or inositol hexakisphosphate] enables us to speculate on the physiological function of these compounds. In this article we focus on two major issues: (1) the roles of inositol high polyphosphates in vesicular trafficking, especially exocytosis, and (2) pleckstrin homology domain-containing IP4 binding proteins involved in the Ras signaling pathway.
Fukuda
M
M
Molecular Neurobiology Laboratory, Tsukuba Life Science Center, Ibaraki, Japan. fukuda@rtc.riken.go.jp
Mikoshiba
K
K
D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000502:physiology; D002966:Clathrin / Q000378:metabolism; D049832:Decapodiformes; D004705:Endocytosis / Q000502:physiology; D005089:Exocytosis / Q000502:physiology; D006801:Humans; D007295:Inositol Phosphates / Q000502:physiology*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D018160:Receptors, Cytoplasmic and Nuclear / Q000502:physiology*; D015290:Second Messenger Systems / Q000502:physiology*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D018631:ras Proteins / Q000502:physiology
D002966:Clathrin; D007295:Inositol Phosphates; D018160:Receptors, Cytoplasmic and Nuclear; C068271:inositol hexakisphosphate receptor; C072844:inositol polyphosphate receptor; C107765:inositol-1,3,4,5,6-pentakisphosphate receptor; C061107:inositol-1,3,4,5-tetrakisphosphate receptor; D018631:ras Proteins; D002118:Calcium