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Characterization of a novel splice variant of phosphatidylinositol 4-Kinase III beta

Monday, October 24, 2011 — Poster Session I

Noon – 2:00 p.m.

Natcher Conference Center




  • N Bojjireddy
  • T Balla


Phosphoinositides (PI) constitute a minor fraction of total cellular phospholipids but they regulate almost every cellular process. Phosphatidylinositol 4-kinase(s) (PI4Ks) catalyze first step in the synthesis of PIs. PI4Ks are classified into type II and type III with a a and b isoforms each. PI4KIIIb is involved in Golgi to plasma membrane secretion but also has been implicated in cytokinesis. Recently PI4KIIIb was found to be essential for enteroviral replication of several small RNA viruses. Here we report on cloning of a novel splice variant of PI4KIIIb(PI4KIIIbS) from a bovine cDNA library that has an extra stretch of serine/threonine rich 15 amino acid sequence located adjacent to the NCS-1 binding region and the PKD phosphorylation site of the enzyme. PKD phosphorylation and NCS-1 association has been shown to regulate the PI4K activity of PI4KIIIb. In situ phosphorylation studies using HA-tagged versions of PI4KIIIb or PI4KIIIbS expressed in HEK19 cells, and labeling with 32P-phosphate, showed comparable phosphorylation of the two forms. Using kinase assays on immunopreceiptated enzymes showed that PI4KIIIbS was catalytically active comparable with PI4KIIIb PI4KIIIbS, similarly to its shorter version, interacted with NCS-1 and Rab11 as assessed with co-immunoprecipitation studies using HA-tagged variants of PI4KIIIb and GFP-tagged-NCS1 or Rab11

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