Abstract
In Saccharomyces cerevisiae, the endoplasmic reticulum (ER) is found along the cell periphery (cortical ER) and nucleus (perinuclear ER). In this study, we characterize a novel ER protein called Ice2p that localizes to the cortical and perinuclear ER. Ice2p is predicted to be a type-III transmembrane protein. Cells carrying a genomic disruption of ICE2 display defects in the distribution of cortical ER in mother and daughter cells. Furthermore, fluorescence imaging of ice2delta cells reveals an abnormal cortical ER tubular network morphology in both the mother cell and the developing bud. Subcellular fractionation analysis using sucrose gradients corroborate the data from the fluorescence studies. Our findings indicate that Ice2p plays a role in forming and/or maintaining the cortical ER network in budding yeast.
Highlights
The endoplasmic reticulum (ER) is a polygonal network of membrane tubules and sheet-like cisternae (Palade, 1956)
We identify a novel integral ER membrane protein called Ice2p, which plays a role in the formation and/or maintenance of the cortical ER tubular network in mother and daughter cells in budding yeast
To identify components that are required for the maintenance or inheritance of the ER, cells expressing the ER marker Hmg1p-green fluorescent protein (GFP) (Du et al, 2001) were mutagenized by randomly inserting a Tn3-based transposon into the yeast genome as described previously (Burns et al, 1994)
Summary
The endoplasmic reticulum (ER) is a polygonal network of membrane tubules and sheet-like cisternae (Palade, 1956). These tubular structures are connected to one another and to the outer nuclear envelope to form a continuous membranous system. The cortical ER forms a network of interconnected tubules that is juxtaposed to the plasma membrane, whereas the perinuclear ER surrounds the nucleus (Prinz et al, 2000) It is complex in structure, the ER in higher eukaryotes is dynamic and undergoes continuous reorganization via the movement of individual tubules, ring closure of the tubular network and the formation of new tubules (Lee and Chen, 1988). The cortical ER undergoes sliding and branching tubule movements, as well as those events reported for mammalian cells (Prinz et al, 2000)
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