Identification and characterization of a novel inositol polyphosphate 5-phosphatase

  • Ijuin T
  • Mochizuki Y
  • Fukami K
 et al. 
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Abstract

We have identified a cDNA encoding a novel inositol polyphosphate 5-phosphatase. It contains two highly conserved catalytic motifs for 5-phosphatase, has a molecular mass of 51 kDa, and is ubiquitously expressed and especially abundant in skeletal muscle, heart, and kidney. We designated this 5-phosphatase as SKIP (Skeletal muscle and Kidney enriched Inositol Phosphatase). SKIP is a simple 5-phosphatase with no other motifs. Baculovirus-expressed recombinant SKIP protein exhibited 5-phosphatase activities toward inositol 1,4,5-trisphosphate, inositol 1,3,4,5-tetrakisphosphate, phosphatidylinositol (PtdIns) 4,5-bisphosphate, and PtdIns 3,4, 5-trisphosphate but has 6-fold more substrate specificity for PtdIns 4,5-bisphosphate (K(m) = 180 microM) than for inositol 1,4, 5-trisphosphate (K(m) = 1.15 mM). The ectopic expression of SKIP protein in COS-7 cells and immunostaining of neuroblastoma N1E-115 cells revealed that SKIP is expressed in cytosol and that loss of actin stress fibers occurs where the SKIP protein is concentrated. These results imply that SKIP plays a negative role in regulating the actin cytoskeleton through hydrolyzing PtdIns 4,5-bisphosphate

Author-supplied keywords

  • actin
  • cDNA
  • cytoskeleton
  • inositol phosphatase
  • kidney
  • muscle
  • neuroblastoma
  • phosphatidylinositol
  • stress
  • substrate

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  • PMID: 10753883

Authors

  • T Ijuin

  • Y Mochizuki

  • K Fukami

  • M Funaki

  • T Asano

  • T Takenawa

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