Mutation of a tyrosine localization signal in the cytosolic tail of yeast Kex2 protease disrupts Golgi retention and results in default transport to the vacuole.

Abstract

Kex2 protease processes pro-alpha-factor in a late Golgi compartment in Saccharomyces cerevisiae. The first approximately 30 residues of the 115 amino acid CO2H-terminal cytosolic tail (C-tail) of the Kex2 protein (Kex2p) contain a Golgi retention signal that resembles coated-pit localization signals in mammalian cell surface receptors. Mutation of one (Tyr713) of two tyrosine residues in the C-tail or deletion of sequences adjacent to Tyr713 results in loss of normal Golgi localization. Surprisingly, loss of the Golgi retention signal resulted in transport of C-tail mutant Kex2p to the vacuole (yeast lysosome), as judged by kinetics of degradation and by indirect immunofluorescence. Analysis of the loss of Kex2 function in vivo after shutting off expression of wild-type or mutant forms proved that mutations that cause rapid vacuolar turnover do so by increasing the rate of exit of the enzyme from the pro-alpha-factor processing compartment. The most likely explanation for these results is that mutation of the Golgi retention signal in the C-tail results in transport of Kex2p to the vacuole by default. Wild-type Kex2p also was transported to the vacuole at an increased rate when overproduced, although apparently not due to saturation of a Golgi-retention mechanism. Instead, the wild-type and C-tail mutant forms of Kex2p may follow distinct paths to the vacuole.

Vps52p, Vps53p, and Vps54p Form a Novel Multisubunit Complex Required for Protein Sorting at the Yeast Late Golgi

“…The localization of a number of resident late Golgi proteins also depends on recycling from the prevacuolar compartment, and a failure to recycle results in transport to the vacuole, where they are degraded (Wilcox et al, 1992;Nothwehr et al, 1993;Cooper and Stevens, 1996). A-ALP is a model late Golgi protein that consists of the membrane and lumenal domains of ALP fused to the cytoplasmic domain of DPAP A, which contains the sorting information required for localization of the chimera to the late Golgi (Nothwehr et al, 1993).…”

Cloning and Subcellular Location of an Arabidopsis Receptor-Like Protein That Shares Common Features with Protein-Sorting Receptors of Eukaryotic Cells

“…In addition, some Tyr motifs have been found to be important for the retention of membrane proteins at the TGN in mammalian and yeast cells (Bos et al, 1993;Voorhees et al, 1995;Wilcox et al, 1992), and, most recently, a Tyr-based targeting signal has been shown to mediate the sorting of an integral membrane glycoprotein into Golgi-derived CCVs (Honing et al, 1996). These cytoplasmic Tyr motifs interact with other components of the sorting machinery, such as the clathrin-associated AP1 adaptor protein complex (Pladaptin,~1 ,and ul) at the TGN.…”

Role of 26S proteasome and HRD genes in the degradation of 3-hydroxy-3-methylglutaryl-CoA reductase, an integral endoplasmic reticulum membrane protein.

“…Some membrane proteins are trafficked to the lysosome or vacuole by vesicular transport (Wilcox et al, 1992;Berkower et al, 1994). In contrast, the destruction of certain endoplasmic reticulum (ER) proteins, such as the CFTR protein, the unassembled T-cell receptor subunits, and 3-hydroxy-3-methylglutaryl-CoA (HMG-R), appears to occur in situ in the ER without the need for traffic to a degradative compartment.…”