Excess production and secretion of very low-density lipoprotein (VLDL) by the liver into the circulatory system is directly related to atherosclerosis, a chronic cardiovascular disease that threatens the lives of many worldwide and continues to be a leading cause of death in the United States. The rate-limiting step in VLDL secretion is its transport from the site of biogenesis, the hepatic endoplasmic reticulum to the cis-Golgi. This step is mediated by a specialized ER- derived vesicle, the VLDL transport vesicle (VTV). Upon exit of the ER the VTV targets, fuses and delivers VLDL into the lumen of the Golgi. The targeting and fusion of the VTV with the Golgi is facilitated by specific set of soluable N-ethylmaleimide sensitive factor attachment protein receptor (SNARE) proteins that form a SNARE complex, which is required for the VTV-Golgi fusion and thus delivery to the Golgi. Data from our laboratory indicates that the formation of the SNARE complex requires cytosolic factors. Through the purification of liver cytosol, chromatographic steps, detailed mass spectrometry, immunodepletion and western blotting data it was identified that the protein necessary for SNARE complex formation is Hsc-70. Although Hsc-70's identification is significant, the role it plays in SNARE complex formation for VTV -Golgi fusion is a predicament and yet to be unraveled. In this study we performed a series of co-immunoprecipitation reactions to identify its role in SNARE-complex assembly. Using western blot data we confirmed binding of Hsc-70 with Sec22b, the v-SNARE on the VTV. Moreover, we confirmed the interaction of Hsc-70 with t-SNAREs, (syn5, rBet1 and GOS28) on the Golgi membrane. Removal of Hsc-70 from the liver cytosol resulted in significant reduction of SNARE-complex formation. Ultimately, the identification proteins involved in the process of VLDL delivery to the Golgi would offer therapeutic targets to control VLDL secretion into the blood by the liver.


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Thesis Completion





Siddiqi, Shadab


Bachelor of Science (B.S.)


Burnett School of Biomedical Sciences

Degree Program

Molecular Biology and Microbiology


Dissertations, Academic -- Medicine;Medicine -- Dissertations, Academic







Access Status

Open Access

Length of Campus-only Access


Document Type

Honors in the Major Thesis