Interruption of Inositol Sphingolipid Synthesis Triggers Stt4p-dependent Protein Kinase C Signaling

• Published in: The Journal of biological chemistry Vol. 285; no. 53; pp. 41947 - 41960
• Main Authors: Jesch, Stephen A., Gaspar, Maria L., Stefan, Christopher J., Aregullin, Manuel A., Henry, Susan A.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 31.12.2010; American Society for Biochemistry and Molecular Biology
• Subjects: 1-Phosphatidylinositol 4-Kinase - metabolism; Biosensing Techniques; Cell Biology; Cell Membrane - metabolism; Enzyme Activation; Gene Expression Regulation, Fungal; Inositol - chemistry; Inositol Phospholipid; Lipid Raft; MAP Kinase Signaling System; MAPKs; Microscopic Imaging; Phenotype; Phosphatidylinositol Signaling; Phospholipid Metabolism; Plasma Membrane; Protein Kinase C (PKC); Protein Kinase C - metabolism; Saccharomyces cerevisiae - genetics; Saccharomyces cerevisiae Proteins - metabolism; Signal Transduction; Sphingolipid; Sphingolipids - chemistry; Temperature; Time Factors; Lipid Raft; Plasma Membrane; Signal Transduction; Protein Kinase C (PKC); Inositol Phospholipid; Sphingolipid; Phosphatidylinositol Signaling; Phospholipid Metabolism; Microscopic Imaging; MAPKs
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M110.188607

The protein kinase C (PKC)-MAPK signaling cascade is activated and is essential for viability when cells are starved for the phospholipid precursor inositol. In this study, we report that inhibiting inositol-containing sphingolipid metabolism, either by inositol starvation or treatment with agents that block sphingolipid synthesis, triggers PKC signaling independent of sphingoid base accumulation. Under these same growth conditions, a fluorescent biosensor that detects the necessary PKC signaling intermediate, phosphatidylinositol (PI)-4-phosphate (PI4P), is enriched on the plasma membrane. The appearance of the PI4P biosensor on the plasma membrane correlates with PKC activation and requires the PI 4-kinase Stt4p. Like other mutations in the PKC-MAPK pathway, mutants defective in Stt4p and the PI4P 5-kinase Mss4p, which generates phosphatidylinositol 4,5-bisphosphate, exhibit inositol auxotrophy, yet fully derepress INO1, encoding inositol-3-phosphate synthase. These observations suggest that inositol-containing sphingolipid metabolism controls PKC signaling by regulating access of the signaling lipids PI4P and phosphatidylinositol 4,5-bisphosphate to effector proteins on the plasma membrane.