High impact information on EMP47

• Putative retrograde carriers (COPI vesicles) generated from Golgi-enriched membranes contain v-SNAREs as well as Emp47p as cargo [1].
• The Saccharomyces cerevisiae EMP47 gene encodes a nonessential type-I transmembrane protein with sequence homology to a class of intracellular lectins defined by ERGIC-53 and VIP36 [2].
• Consistent with this finding, the Ste2p-Emp47p hybrid protein was mislocalized to the cell surface in the alpha-COP mutant, ret1-1 [2].
• Thus Emp47p cycles between the Golgi apparatus and the ER and requires a di-lysine motif for its alpha-COP-independent, steady state localization in the Golgi [2].
• To investigate whether Emp47p undergoes retrograde transport from the Golgi to the ER like other di-lysine-tagged proteins we developed an assay to measure this step after block of forward transport in a sec12 mutant [2].

Biological context of EMP47

• The effect of high temperature on Emp47p localization, as well as the temperature sensitivity of the mutant strain on rich medium, appear to be caused by oxidative stress and are correlated with severe reductions in the intracellular levels of low-molecular-weight thiols [3].
• The yeast open reading frame YLR080w/EMP46 encodes a homolog of the Golgi protein Emp47p [4].
• The protein is degraded more rapidly in cells with a point mutation in the WD40 domain of beta'-COP (sec27-95) or in cells lacking the domain altogether, whereas a point mutation in the Clathrin Heavy Chain Repeat (sec27-1) does not affect the turnover of Emp47p [5].

Anatomical context of EMP47

• We showed by immunofluorescence, sucrose-gradient analysis and quantitative Western analysis that the mutant mislocalized Emp47p to the vacuole at high temperature, while Golgi structures were apparently normal and biosynthetic routing of the vacuolar carboxypeptidase Y (CPY) and the plasma membrane GPI-anchored protein Gas1p were unaffected [3].
• We propose that Emp46p and Emp47p are required for the export of specific glycoprotein cargo from the endoplasmic reticulum [4].
• The di-lysine motif of Emp47p was functional when transplanted onto Ste2p, a plasma membrane protein, conferring ER localization [2].

Associations of EMP47 with chemical compounds

• Dilysine-dependent Golgi localization of Emp47p was also defective in both mutants [6].
• In accordance with this conclusion, cys3-2 mutant cells were more sensitive to the oxidizing agent 1-chloro-2,4-dinitrobenzene, which also aggravated the mislocalization of Emp47p observed at high temperature [3].
• Emp47p and its close homolog Emp46p have a tyrosine-containing endoplasmic reticulum exit signal and function in glycoprotein secretion in Saccharomyces cerevisiae [4].

Other interactions of EMP47

• Furthermore we have characterized three new alleles of ret1 and showed that Golgi localization of Emp47p was intact in cells with those mutant alleles [7].
• In contrast to results with alpha-COP mutants, we found that Emp47p was mislocalised to the vacuole in mutants affecting beta'-, gamma-, delta-, and zeta-COP subunits of coatomer and that the mutant coatomer bound neither to the Emp47p nor to the Wbp1p di-lysine signal in vitro [7].

References