The orphan P5-ATPase Spf1 changes the requirement of amino acid for optimal growth

M. CLARA SELLES; N. SARBIA; M. LUCÍA BLANCO; G. R. CORRADI; HUGO P. ADAMO

Buenos aires

Congreso; II International Congress in Translational Medicine; 2015

P5 -type ATPases comprise a large family of proteins, present in prokaryotic and eukaryotic cells whose function at the molecular level is unknown (1). Their homology to other P-ATPases suggests that they catalyze active transport of an unknown substrate through cell membranes. Five genes code for P5-ATPases in humans, the loss of function of the human P5B ATPase ATP13a2 is cause of neurodegeneration associated with the development of an early form of the Parkinsonism known as Kufor-Rakeb syndrome and lipofuscinonis juvenile, while mutations in the ATP13a4 gene have been related to autism and language delay. The yeast Saccharomyces cerevisiae (Sc) contains two genes that code for P5-ATPases: Yel031w coding for Spf1p, and Yor291w coding for Ypk9. The Spf1p is localized in the ER membrane while the Ypk9 is present in the yeast vacuole membrane. The lack of functional Spf1p causes a phenotype consistent with an ER dysfunction, including a defect in protein glycosylation. Recently the importance of the P5-ATPases in the function of the endosomal-lysosomal system has been demonstrated (2). With the aim of gaining further insight of the Spf1p function we have investigated the phenotypic characteristics of ∆Spf1p cells under nitrogen starvation conditions. Despite the apparently relevant functions of Spf1p, the proliferation of ∆Spf1p cells under standard growth conditions was seemingly normal. However we found that ∆Spf1p cells require higher concentrations of amino acids for optimal growth. Expression of Spf1p from a plasmid or increasing the supplementation of amino acids in the growth medium helped to restore the normal response of ∆Spf1p cells. Because under nitrogen limitation the supply of amino acids by autophagy becomes essential for normal protein biosynthesis and growth (2), these results may indicate a possible function of Spf1p in autophagy.