Interaction with Btn2p Is Required for Localization of Rsg1p: Btn2p-Mediated Changes in Arginine Uptake in Saccharomyces cerevisiae

Abstract

Btn2p, a novel coiled-coil protein, is up-regulated in btn1⌬ yeast strains, and this up-regulation is thought to contribute to maintaining a stable vacuolar pH in btn1⌬ strains (D. A. Pearce, T. Ferea, S. A. Nosel, B. Das, and F. Sherman, Nat. Genet. 22:55-58, 1999). We now report that Btn2p interacts biochemically and functionally with Rsg1p, a down-regulator of the Can1p arginine and lysine permease. Rsg1p localizes to a distinct structure toward the cell periphery, and strains lacking Btn2p (btn2⌬ strains) fail to correctly localize Rsg1p. btn2⌬ strains, like rsg1⌬ strains, are sensitive for growth in the presence of the arginine analog canavanine. Furthermore, btn2⌬ strains, like rsg1⌬ strains, demonstrate an elevated rate of uptake of [ 14 C]arginine, which leads to increased intracellular levels of arginine. Overexpression of BTN2 results in a decreased rate of arginine uptake. Collectively, these results indicate that altered levels of Btn2p can modulate arginine uptake through localization of the Can1p-arginine permease regulatory protein, Rsg1p. Our original identification of Btn2p was that it is up-regulated in the btn1⌬ strain which serves as a model for the lysosomal storage disorder Batten disease. Btn1p is a vacuolar/lysosomal membrane protein, and btn1⌬ suppresses both the canavanine sensitivity and the elevated rate of uptake of arginine displayed by btn2⌬ rsg1⌬ strains. We conclude that Btn2p interacts with Rsg1p and modulates arginine uptake. Up-regulation of BTN2 expression in btn1⌬ strains may facilitate either a direct or indirect effect on intracellular arginine levels.

Normal levels of the antiprion proteins Btn2 and Cur1 cure most newly formed [URE3] prion variants

“…We found that Btn2p was consistently concentrated in one or two dots close to the nucleus (17). Btn2p mediates late endosome-Golgi protein movements (49) and affects several proteins processed by this system (49)(50)(51). Nonetheless, the relation of the different activities of Btn2p remains unclear.…”

Btn2, a Hook1 Ortholog and Potential Batten Disease-Related Protein, Mediates Late Endosome-Golgi Protein Sorting in Yeast

“…Previous studies have shown that Btn2 interacts with a wide variety of proteins (i.e., Rhb1, Yif1, and Ist2) (13,14,43) purportedly involved in numerous processes relevant to cell growth and homeostasis (i.e., ion, pH, or amino acid balance). However, the precise role of Btn2 in intracellular membrane transport has remained obscure.…”

“…5A), as previously shown (14,51). We examined Yif1 localization in a variety of cell types, including cells lacking BTN2 or RSG/RHB1, a small GTPase of unknown function (83) that was found to interact with Btn2, using the yeast two-hybrid screen (13). Interestingly, instead of the punctate labeling seen in wild-type cells, GFP-Yif1 was found to accumulate in the vacuole in both btn2⌬ and rhb1⌬ cells ( Fig.…”

The Human Synaptic Vesicle Protein, SV2A, Functions as a Galactose Transporter in Saccharomyces cerevisiae

“…Galactose transport was measured by using techniques adapted from Chattopadhyay and Pearce (13). Each experiment was repeated independently 3-4 times to determine statistical significance.…”