Characterizing Functional Roles of Sec61 Complex in Collagen Turnover

Fibrosis is a pathological condition in which the imbalance between collagen production and collagen degradation leads to excessive deposition of collagen-rich matrix in the interstitial space. Several identified pathways are mainly focused on the collagen production preceding fibrosis, but the pathways involved collagen uptake and intracellular degradation are poorly characterized. Through a genome-wide dsRNA-mediated screen in Drosophila S2 cells, we identified 22 candidate genes that are required for efficient internalization of type I collagen in insect cells. One of the 22 candidate genes, Sec61beta, is a subunit of Sec61 translocon complex which is an endoplasmic reticulum (ER)-resident multimeric complex (alpha, beta, and gamma subunits), and allows the transport of secreted and transmembrane proteins across lipid bilayers. Our flow cytometry data showed that Sec61 complex knockdown leads to an increase of the internalized collagen in monocyte/macrophage U937 cells. Interestingly, Sec61 complex knockdown also increases the expression level of BIP, an ER stress marker, which drives us to speculate which mechanisms or pathways of the ER stress and UPR response Sec61 complex is involved in. In the proposed studies, we will characterize the functional roles of Sec61 complex in collagen degradation and sorting/accumulation in monocytes/macrophages. We will further verify which pathway(s) in ER stress and UPR response that is induced by excessively internalized collagen in the absence of Sec61 complex in monocytes/macrophages. In this manner, we will identify novel pathways and mechanisms that mediate cellular uptake and turnover of collagen. The proposed studies will be critical in establishing an innovative concept to study collagen turnover.

Project ID:PC10608-1821
External Project ID:MOST106-2320-B182-016