Surf4 (Erv29p) binds amino-terminal tripeptide motifs of soluble cargo proteins with different affinities, enabling prioritization of their exit from the endoplasmic reticulum

by Ying Yin, Mekka R. Garcia, Alexander J. Novak, Allison M. Saunders, Raira S. Ank, Anna S. Nam, Larry W. Fisher

Some secreted proteins that assemble into large complexes, such as extracellular matrices or hormones and enzymes in storage granules, must be kept at subaggregation concentrations during intracellular trafficking. We show surfeit locus protein 4 (Surf4) is the cargo receptor that establishes different steady-state concentrations for a variety of soluble cargo proteins within the endoplasmic reticulum (ER) through interaction with the amino-terminal tripeptides exposed after removal of leader sequences. We call this motif the ER-Exit by Soluble Cargo using Amino-terminal Peptide-Encoding motif (ER-ESCAPE motif). Proteins that most readily aggregate in the ER lumen (e.g., dentin sialophosphoprotein [DSPP] and amelogenin, X-linked [AMELX]) have strong ER-ESCAPE motifs to inhibit aggregate formation, while less susceptible cargo exhibits weaker motifs. Specific changes in a single amino acid of the tripeptide result in aggregate formation and failure to efficiently traffic cargo out of the ER. A logical subset of 8,000 possible tripeptides starting a model soluble cargo protein (growth hormone) established a continuum of steady-state ER concentrations ranging from low (i.e., high affinity for receptor) to the highest concentrations associated with bulk flow–limited trafficking observed for nonbinding motifs. Human cells lacking Surf4 no longer preferentially trafficked cargo expressing strong ER-ESCAPE motifs. Reexpression of Surf4 or expression of yeast’s ortholog, ER-derived vesicles protein 29 (Erv29p), rescued enhanced ER trafficking in Surf4-null cells. Hence our work describes a new way of preferentially exporting soluble cargo out of the ER that maintains proteins below the concentrations at which they form damaging aggregates.

Source link

Related posts

Low thermal dependence of the contractile properties of a wing muscle in the bat Carollia perspicillata [RESEARCH ARTICLE]


Voltages and resistances of the anterior Malpighian tubule of Drosophila melanogaster [RESEARCH ARTICLE]


Virus batteries


This website uses cookies to improve your experience. We'll assume you're ok with this, but you can opt-out if you wish. Accept Read More

Privacy & Cookies Policy


COVID-19 (Coronavirus) is a new illness that is having a major effect on all businesses globally LIVE COVID-19 STATISTICS FOR World