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Endoplasmic Reticulum Exit of a Secretory Glycoprotein in the Absence of Sec24p Family Proteins in Yeast
Author(s) -
Karhinen Leena,
Bastos Ricardo Nunes,
Jokitalo Eija,
Makarow Marja
Publication year - 2005
Publication title -
traffic
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.677
H-Index - 130
eISSN - 1600-0854
pISSN - 1398-9219
DOI - 10.1111/j.1600-0854.2005.00297.x
Subject(s) - copii , endoplasmic reticulum , biology , secretory protein , secretion , glycoprotein , microbiology and biotechnology , secretory pathway , mutant , copi , saccharomyces cerevisiae , yeast , vesicle , golgi apparatus , gene , biochemistry , membrane
Glycoproteins exit the endoplasmic reticulum (ER) of the yeast Saccharomyces cerevisiae in coàt protein complex II (COPII) coated vesicles. The coat consists of the essential proteins Sec23p, Sec24p, Sec13p, Sec31p, Sar1p and Sec16p. Sec24p and its two nonessential homologues Sfb2p and Sfb3p have been suggested to serve in cargo selection. Using temperature‐sensitive sec24‐1 mutants, we showed previously that a secretory glycoprotein, Hsp150, does not require functional Sec24p for ER exit. Deletion of SFB2 , SFB3 or both from wild type or the deletion of SFB2 from sec24‐1 cells did not affect Hsp150 transport. SFB3 deletion has been reported to be lethal in sec24‐1 . However, here we constructed a sec24‐1 Δ sfb3 and a sec24‐1 Δ sfb2 Δ sfb3 strain and show that Hsp150 was secreted slowly in both. Turning off the SEC24 gene did not inhibit Hsp150 secretion either, and the lack of SEC24 expression in a Δ sfb2 Δ sfb3 deletant still allowed some secretion. The sec24‐1 Δ sfb2 Δ sfb3 mutant grew slower than sec24‐1 . The cells were irregularly shaped, budded from random sites and contained proliferated ER at permissive temperature. At restrictive temperature, the ER formed carmellae‐like proliferations. Our data indicate that ER exit may occur in vesicles lacking a full complement of Sec23p/24p and Sec13p/31p, demonstrating diversity in the composition of the COPII coat.