The Role of Phosphoinositide Metabolism in the Regulation of Neuronal Activity

Phosphoinositides are a rare family of phospholipids present in the majority of mammalian cells. Prior studies have established the importance of phosphoinositides in the regulation of neuronal activity; specifically in action potential firing, the release and reuptake of neurotransmitters, and axonal growth. In order to identify regulatory mechanisms in the biochemical network involved in phosphoinositide metabolism, the Kruse research group conducted an RNA-Seq screen on two genetically modified human embryonic kidney (HEK293) cell lines. PITPNA-KO cells lack a lipid transfer protein involved in one of the earliest steps of phosphoinositide synthesis, while PIP5K1C-KO cells lack a lipid kinase involved in the last step in the synthesis pathway of phosphatidylinositol 4,5-bisphosphate, the phosphoinositide most critical for the regulation of neuronal activity. With recent evidence shedding light on the role of long non-coding RNAs (lncRNAs) in the expression of genes correlated with lipid production, this project utilizes data from the aforementioned RNA-Seq screen to identify lncRNAs involved in the regulation of genes associated with phosphoinositide metabolism. A validation of RNA-Seq data by RT-qPCR confirmed altered expression levels of several genes. Finally, protein expression analysis by Western blot was used to analyze potentially increased or decreased protein levels in correlation with altered mRNA levels. These experiments identified a significant up-regulation of GPR132 and down-regulation of NIBAN1 and CCDC187 in HEK293-PITPNA-KO cells while the expression levels of these proteins were unaltered in HEK293-PIP5K1C-KO cells. In conclusion, this study identified NIBAN1, GPR132, and CCDC187 as genes with a previously unknown connection to phosphoinositide metabolism