Degradation of Saccharomyces cervisiae Rck2 upon exposure of cells to high levels of zinc is dependent on Pep4.
In undisturbed cells, the MAPK-activated protein kinase Rck2 of Saccharomyces cerevisiae is a stable protein with a turnover time exceeding 60 min. However, we have found that Rck2 is subject to intracellular degradation after exposure of cells to Zn2+ concentrations of 5 mM or more. In high-zinc medium, most of the Rck2 pool is degraded within 5 min. This degradation is blocked by inhibiting the vacuolar proteolytic pathway with the protease inhibitor phenyl methyl sulphonyl fluoride or by mutation of the PEP4 gene. By contrast, blocking the proteasomal pathway with the inhibitor MG132 does not prevent Rck2 degradation upon addition of Zn2+, nor is degradation inhibited in the proteasomal mutations pre1 pre2, cim3, or cim5. The stability of Rck2 is not affected by any of the other stress conditions examined, or by growth rate. Possible mechanisms of the degradation of Rck2 under high zinc conditions, and its physiological significance, are discussed.
Swaminathan
Swarna
S
Lundberg Laboratory, Department of Cell and Molecular Biology, Göteborg University, P.O. Box 462, 405 30, Goteborg, Sweden.
Sunnerhagen
Per
P
D016282:Aspartic Acid Endopeptidases / Q000378:metabolism*; D015153:Blotting, Western; D049109:Cell Proliferation; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D003593:Cytoplasm / Q000378:metabolism; D005838:Genotype; D007976:Leupeptins / Q000494:pharmacology; D020935:MAP Kinase Signaling System; D009154:Mutation; D010447:Peptide Hydrolases / Q000378:metabolism; D010664:Phenylmethylsulfonyl Fluoride / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D013997:Time Factors; D014617:Vacuoles / Q000378:metabolism; D015032:Zinc / Q000737:chemistry / Q000378:metabolism*
D015853:Cysteine Proteinase Inhibitors; D007976:Leupeptins; D029701:Saccharomyces cerevisiae Proteins; D010664:Phenylmethylsulfonyl Fluoride; C407464:RCK2 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases; D010447:Peptide Hydrolases; C022325:aspartic proteinase A; D016282:Aspartic Acid Endopeptidases; D046988:Proteasome Endopeptidase Complex; D015032:Zinc; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde