Differential effects of Sec61α-, Sec62- and Sec63-depletion on transport of polypeptides into the endoplasmic reticulum of mammalian cells

Abstract

SummaryCo-translational transport of polypeptides into the endoplasmic reticulum (ER) involves the Sec61 channel and additional components such as the ER lumenal Hsp70 BiP and its membrane-resident co-chaperone Sec63p in yeast. We investigated whether silencing the SEC61A1 gene in human cells affects co-and post-translational transport of presecretory proteins into the ER and post-translational membrane integration of tail-anchored proteins. Although silencing the SEC61A1 gene in HeLa cells inhibited co-and post-translational transport of signal-peptide-containing precursor proteins into the ER of semi-permeabilized cells, silencing the SEC61A1 gene did not affect transport of various types of tail-anchored protein. Furthermore, we demonstrated, with a similar knockdown approach, a precursor-specific involvement of mammalian Sec63 in the initial phase of co-translational protein transport into the ER. By contrast, silencing the SEC62 gene inhibited only post-translational transport of a signal-peptide-containing precursor protein.

Translocon component Sec62 acts in endoplasmic reticulum turnover during stress recovery

“…8f). Altogether, these data show that the LIR motif of Sec62 is required and sufficient for delivery of ER portions to autolysosomes and that in contrast to its role in protein translocation 9,10 (Fig. 4h and Extended data Fig.…”

“…This novel role of Sec62 in ER physiology is enhanced after successful resolution of ER stress, contribute to re-establish pre-stress ER homeostasis and opens several lines of research aiming at better understanding of how mammalian cells maintain or re-establish proteostasis. The activity of Sec62 in translocation of nascent proteins across the ER membrane is carried out in complex with Sec63 and requires formation of higher order complexes with other components of the Sec61 translocon 9,10,[12][13][14][15] . However, ectopic expression of Sec62 or of reporter proteins displaying its LIR containing cytosolic domain is sufficient to enhance delivery of ER protein markers to the autolysosomal system for clearance, and Sec63 is not required for Sec62 function in ER stress recovery.…”

“…6a, b). Sec62 is an ER-resident protein with a well-established role in post-translational protein import in the ER that obligatorily depends on formation of Sec62:Sec63 heterodimeric complexes in association with the Sec61 translocon 9,10 . The LIR motif of Sec62 adapts to the LC3 protein-binding groove establishing specific contacts according to docking and molecular dynamics simulations ( Fig.…”

Essential Role of X-Box Binding Protein-1 during Endoplasmic Reticulum Stress in Podocytes

“…These were mated with Podocin-Cre mice to generate a podocyte-specific DKO of Sec63 and Xbp1 (Pod-Sec63/Xbp1 DKO). Tail genotyping was performed by PCR using previously described protocols for Xbp1 12,13 and Sec63, 9,11 Pod-Sec63/Xbp1 DKO mice (homozygous for the floxed Sec63 and Figure 6. Pod-Sec63/Xbp1 DKO mice glomeruli have increased apoptosis.…”

Interaction ofPseudomonas aeruginosaExotoxin A with the human Sec61 complex suppresses passive calcium efflux from the endoplasmic reticulum

“…3,14,16 the Bip-Sec63 interaction was described by tyedmers et al and the effect of the r197e mutation by awad et al 17,18 So far, the latter interaction as well as the Sec62-Sec63 interaction were found to be relevant only for protein transport into the er, i.e., gating of the Sec61 complex from the closed to the open conformation; 19 in contrast, the Bip co-chaperone for gating to the closed state is still elusive. 3 See text for details.…”