The Golgi complex is a ubiquitous eukaryotic organelle that plays a central role in post-translational processing and sorting of newly synthesized proteins and lipids. One of the best-studied functions of the Golgi complex is oligosaccharide processing, which is precisely controlled by expression and localization of glycosyltransferases and glycosidases. Glycosylation patterns change during development, and aberrant glycosylation patterns may contribute to metastasis of tumor cells. The sorting function of the Golgi complex is also critical, since protein and lipid mistargeting can lead to disease. In mammalian cells, the Golgi complex has an unusual structure consisting of sets of stacked cisternal membranes gathered into a ribbon near the cell nucleus. The function of this elaborate structure is not known. Peripheral Golgi membrane proteins with large coiled-coil domains called golgins have been implicated in Golgi structure and function. Previous work has shown that golgin-160 is required for efficient sorting of certain cargo molecules, including the beta-1 adrenergic receptor and the glucose transporter GLUT4. Golgin-160 is also an early target for cleavage by caspases after pro-apoptotic stimuli, suggesting that the trafficking function may be rapidly inactivated during cellular stress. Using golgin-160 as a model, the coupling of cargo traffic, stress sensing and Golgi structure will be explored.
The specific aims of the project are to: (1) Test the hypothesis that interaction of golgin-160 with specific cargo molecules is required for their efficient post-Golgi sorting by determining the mechanism by which golgin-160 functions in cargo trafficking;(2) Determine the mechanism by which a caspase-resistant version of golgin-160 disrupts membrane trafficking steps required for cellular response to stress;and (3) Test the hypothesis that cleavage of golgins by Golgi- localized caspase-2 is required for response to specific stresses by using drugs that target the Golgi complex, measuring local activation of caspase-2 at Golgi membranes, and determining the consequences of blocking nuclear accumulation of golgin cleavage fragments. These studies will enhance the understanding of Golgi structure and how it relates to Golgi function in mammalian cells, and potentially uncover a novel signaling pathway from the Golgi to the nucleus.
The Golgi complex is a ubiquitous cellular organelle that is instrumental for delivering cargo molecules to the cell surface. Golgin-160 is a Golgi resident protein that is implicated in proper surface delivery of molecules that impact heart disease and diabetes, and it is also proteolytically cleaved early after insults that lead to cell death. The proposed experiments on golgin-160 will add to our understanding of cargo delivery to the cell surface and to the role of the Golgi complex in transducing stress signals to the rest of the cell.
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