Rtn1p is involved in structuring the cortical endoplasmic reticulum.
The endoplasmic reticulum (ER) contains both cisternal and reticular elements in one contiguous structure. We identified rtn1Delta in a systematic screen for yeast mutants with altered ER morphology. The ER in rtn1Delta cells is predominantly cisternal rather than reticular, yet the net surface area of ER is not significantly changed. Rtn1-green fluorescent protein (GFP) associates with the reticular ER at the cell cortex and with the tubules that connect the cortical ER to the nuclear envelope, but not with the nuclear envelope itself. Rtn1p overexpression also results in an altered ER structure. Rtn proteins are found on the ER in a wide range of eukaryotes and are defined by two membrane-spanning domains flanking a conserved hydrophilic loop. Our results suggest that Rtn proteins may direct the formation of reticulated ER. We independently identified Rtn1p in a proteomic screen for proteins associated with the exocyst vesicle tethering complex. The conserved hydophilic loop of Rtn1p binds to the exocyst subunit Sec6p. Overexpression of this loop results in a modest accumulation of secretory vesicles, suggesting impaired exocyst function. The interaction of Rtn1p with the exocyst at the bud tip may trigger the formation of a cortical ER network in yeast buds.
De Craene
Johan-Owen
JO
Department of Cell Biology and Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06510, USA.
Coleman
Jeff
J
Estrada de Martin
Paula
P
Pypaert
Marc
M
Anderson
Scott
S
Yates
John R
JR
Ferro-Novick
Susan
S
Novick
Peter
P
D004721:Endoplasmic Reticulum / Q000378:metabolism / Q000648:ultrastructure*; D017353:Gene Deletion; D007425:Intracellular Membranes / Q000378:metabolism; D008565:Membrane Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D026901:Membrane Transport Proteins; D015388:Organelles / Q000378:metabolism / Q000648:ultrastructure; D040901:Proteomics; D000069816:SEC Translocation Channels; D012441:Saccharomyces cerevisiae / Q000737:chemistry / Q000235:genetics / Q000648:ultrastructure*; D029701:Saccharomyces cerevisiae Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D022142:Secretory Vesicles / Q000378:metabolism
D008565:Membrane Proteins; D026901:Membrane Transport Proteins; C505725:Rtn1 protein, S cerevisiae; D000069816:SEC Translocation Channels; C499383:SEC61 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins