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The yeast mutant vps5Δ affected in the recycling of Golgi membrane proteins displays an enhanced vacuolar Mg2+/H+ exchange activity

Lookup NU author(s): Dr Gilles Borrelly

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Abstract

Growth of the yeast vacuolar protein-sorting mutant vps5Δ affected in the endosome-to-Golgi retromer complex was more sensitive to Mg2+-limiting conditions than was the growth of the wild-type (WT) strain. This sensitivity was enhanced at acidic pH. The vps5Δ strain was also sensitive to Al3+, known to inhibit Mg2+ uptake in yeast cells. In contrast, it was found to be resistant to Ni2+ and Co2+, two cytotoxic analogs of Mg2+. Resistance to Ni2+ did not seem to result from the alteration of plasma-membrane transport properties because mutant and WT cells displayed similar Ni2+ uptake. After plasma-membrane permeabilization, intracellular Ni2+ uptake in vps5Δ cells was 3-fold higher than in WT cells, which is consistent with the implication of the vacuole in the observed phenotypes. In reconstituted vacuolar vesicles prepared from vps5Δ, the rates of H+ exchange with Ni2+, Co2+, and Mg2+ were increased (relative to WT) by 170%, 130%, and 50%, respectively. The rates of H+ exchange with Ca2+, Cd2+, and K+ were similar in both strains, as were α-mannosidase and H+-ATPase activities, and SDS/PAGE patterns of vacuolar proteins. Among 14 other vacuolar protein-sorting mutants tested, only the 8 mutants affected in the recycling of trans-Golgi network membrane proteins shared the same Ni2+ resistance phenotype as vps5Δ. It is proposed that a trans-Golgi network Mg2+/H+ exchanger, mislocalized to vps5Δ vacuole, could be responsible for the phenotypes observed in vivo and in vitro.

Publication metadata

Author(s): Borrelly G, Boyer J-C, Touraine B, Szponarski W, Rambier M, Gibrat R

Publication type: Article

Publication status: Published

Journal: Proceedings of the National Academy of Sciences of the United States of America

Year: 2001

Volume: 98

Issue: 17

Pages: 9660-9665

ISSN (print): 0027-8424

ISSN (electronic):

Publisher: National Academy of Sciences

URL: http://dx.doi.org/10.1073/pnas.161215198

DOI: 10.1073/pnas.161215198

PubMed id: 11493679

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