A Genetic Screen for Aminophospholipid Transport Mutants Identifies the Phosphatidylinositol 4-Kinase, Stt4p, as an Essential Component in Phosphatidylserine Metabolism

• Published in: The Journal of biological chemistry Vol. 273; no. 21; pp. 13189 - 13196
• Main Authors: Trotter, Pamela J., Wu, Wen-I, Pedretti, John, Yates, Rachel, Voelker, Dennis R.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 22.05.1998; American Society for Biochemistry and Molecular Biology
• Subjects: 1-Phosphatidylinositol 4-Kinase - genetics; 1-Phosphatidylinositol 4-Kinase - metabolism; ACTIVIDAD ENZIMATICA; ACTIVITE ENZYMATIQUE; Biological Transport; CARBOXY-LYASES; Carrier Proteins - genetics; Carrier Proteins - metabolism; CEFALINAS; CEPHALINE; CEPHALINS; COMPLEMENTATION; ENZYMIC ACTIVITY; FENOTIPOS; GENE; GENES; Genetic Complementation Test; GENETIC TRANSFORMATION; GENETICA; GENETICS; GENETIQUE; LIASAS; LIPID METABOLISM; LYASE; LYASES; METABOLISME DES LIPIDES; METABOLISMO DE LIPIDOS; MUTACION; Mutagenesis; MUTANT; MUTANTES; MUTANTS; MUTATION; PHENOTYPE; PHENOTYPES; PHOSPHATIDYLSERINE DECARBOXYLASE; Phosphatidylserines - biosynthesis; Phosphatidylserines - metabolism; PSTB1 GENE; SACCHAROMYCES CEREVISIAE; Saccharomyces cerevisiae - enzymology; Saccharomyces cerevisiae - metabolism; Saccharomyces cerevisiae Proteins; STRUCTURAL GENES; STT4 GENE; Subcellular Fractions - enzymology; Subcellular Fractions - metabolism; TRANSFERASAS; TRANSFERASE; TRANSFERASES; TRANSFORMACION GENETICA; TRANSFORMATION GENETIQUE
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.273.21.13189

In an effort to understand molecular mechanisms of intracellular lipid transport, we have focused upon specific events required for de novo aminophospholipid synthesis in the yeast Saccharomyces cerevisiae. A genetic system for examining the steps between phosphatidylserine (PtdSer) synthesis in the endoplasmic reticulum and its transport to and decarboxylation by PtdSer decarboxylase 2 in the Golgi/vacuole has been developed. We have isolated a mutant, denoted pstB1, that accumulates PtdSer and has diminished phosphatidylethanolamine formation despite normal PtdSer decarboxylase 2 activity. The lesion in PtdSer metabolism is consistent with a defect in interorganelle lipid transport. A genomic DNA clone that complements the mutation was isolated, and sequencing revealed that the clone contains the STT4 gene, encoding a phosphatidylinositol 4-kinase. The pstB1 mutant exhibits a defect in Stt4p-type phosphatidylinositol 4-kinase activity, and direct gene replacement indicates that STT4 is the defective gene in the mutant. Creation of an STT4 null allele (stt4Δ::HIS3) demonstrates the gene is essential. These results provide evidence that implicates phosphoinositides in the regulation of intracellular aminophospholipid transport.