Poster abstracts
Poster number 6 submitted by Marcos Corchado
The role of lpr-3 as a cell non-autonomous activator of oncogenic let-60/Ras in C. elegans
Marcos Corchado (Molecular Genetics, The Ohio State University), Komal Rombani (Biomedical Sciences Graduate Program, The Ohio State University), Gustavo Leone (Biochemistry and Molecular Biology Department, Medical University of South Carolina), Helen Chamberlin (Molecular Genetics, The Ohio State University)
Abstract:
Extracellular signals from the stroma are required for the maintenance and progression of cancer cells. However, identifying such factors is particularly challenging due to the complexity of stromal cell types in mammals. A recent screen performed in a simpler system, the nematode C. elegans, identified lipocalin-related 3 (lpr-3) as a candidate for such a signal. lpr-3 is expressed in mesodermal tissue but is required for let-60/Ras-mediated hyperproliferation of a set of epithelial cells known as the vulva precursor cells (VPCs). Moreover, most lipocalins transport hydrophobic ligands and initiate signaling cascades by binding to specific membrane receptors. The first aim of my research is to identify the receptor of LPR-3. It is known that human lipocalins are endocytosed after binding to a receptor to perform their function. To test if LPR-3 functions through a similar mechanism, I inhibited receptor-mediated endocytosis in the VPCs by performing a VPC-specific RNAi knockdown of clathrin on let-60(gf) animals. Results show a significant suppression of hyperproliferation, which supports the hypothesis that an LPR-3 receptor is present. Subsequently, we performed a literature review to identify candidate receptors. Human Lipocalin-2 was found to function similarly to LPR-3 and binds to a member of solute carrier protein family (SLC) of membrane receptors. Thus, I performed VPC-specific RNAi knockdown experiments for 239 out of 364 C. elegans SLC genes on let-60(gf) animals. In particular, the gene pitr-1 was found to partially suppress hyperproliferation. We hypothesize that partial suppression might be due to the presence of a redundant receptor and suggest performing double RNAi knockdown experiments with pitr-1 and candidates as future work. As an alternative approach, I am performing a genome-wide VPC-specific RNAi screen on let-60(gf) animals to identify potential receptors and downstream effectors of LPR-3. These results fit a model in which LPR-3 binds to PITR-1 and is endocytosed to promote let-60(gf) hyperproliferation. A genome-wide screen for LPR-3 receptors and downstream effectors has been completed for chromosome I and yielded 40 candidates thus far.
Keywords: C elegans, Ras, lpr-3