PtdIns 4-kinase beta and neuronal calcium sensor-1 co-localize but may notdirectly associate in mammalian neurons

It was recently demonstrated that the yeast homologue of phosphatidylinosit ol 4-kinase beta PIK1 is directly associated with frq1, the yeast homologue of mammalian neuronal calcium sensor-1 (NCS-1) (Hendricks et al., [1999] N at. Cell Biol. 1:234- 241). This was a novel finding and suggests that a ca lcium binding protein activates and regulates Ptdlns 4-kinase beta. This fi nding had not been shown in mammalian cells and both Ptdlns 4-kinase beta a nd NCS-1 have been shown to have important roles in the regulation of exocy totic release associated with neurotransmission. The aims of this study wer e to determine if Ptdlns 4-kinase beta and NCS-1 directly associate in mamm alian neural tissues. We show that the immunostaining pattern for Ptdlns 4- kinase beta and NCS-1 is co-localized throughout the neurites of newborn cu ltured dorsal root ganglia (DRG) neurons but not in E13 DRG neurons. We the n provide biochemical evidence that Ptdlns 4-kinase beta may not be in phys ical association with NCS-1 in mammalian nervous tissue unlike that previou sly reported in yeast. (C) 2000 Wiley-Liss, Inc.