Dissecting the role of GPR34 in cDC1 migration and function

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PROJECT SUMMARY/ABSTRACT As critical mediators of immunity against intracellular pathogens and cancer, type 1 conventional dendritic cells (cDC1s) cross-present exogenous, cell-associated antigens to CD8+ T cells, facilitated by the colocalization of these two cell types in the T cell zone of secondary lymphoid tissues. This microanatomical organization is orchestrated by CCR7 and XCR1, two G protein-coupled receptors (GPCRs) on cDC1s that guide their migration towards gradients of chemoattractant ligand. Recent reports have established a crucial role for tumor-associated cDC1s in cancer immunity. However, the GPCRs mediating cDC1 recruitment and positioning at sites of inflammation and in tumors are incompletely understood. Preliminary work has revealed that GPR34, an understudied X-linked GPCR, is highly expressed by cDC1s, and in vitro studies have shown that this lysophosphatidylserine (lysoPS)-responsive receptor supports cell migration. Preliminary data presented herein indicate that GPR34 promotes the accumulation of cDC1s in the inflamed mouse peritoneal cavity (PerC) in a cell-intrinsic manner. The PerC is a clinically important site for colon and ovarian cancer metastasis. In a preliminary experiment inspired by the connection between cDC1 accumulation and cancer outcomes, GPR34-deficiency led to increased growth of a subcutaneous (SQ) tumor model. This proposal will test the hypothesis that GPR34 regulates cDC1 organization and function during inflammation and cancer. Aim 1 will mechanistically define how GPR34 controls the abundance, trafficking, and positioning of PerC cDC1s using a combination of techniques including in vivo kinetic immune phenotyping, in vitro migration assays, and immunofluorescence microscopy. Aim 2 will investigate the role of GPR34 and lysoPS in cancer immunity using ectopic SQ and PerC tumor models along with tools to study antigen-specific T cell responses and to manipulate ligand levels. Completion of these Aims will elucidate key mechanisms by which GPR34 on cDC1s influences the response to inflammation and malignancy, providing opportunities for the development of therapeutics that modulate the lysoPS-GPR34 chemoattractant system. These research goals will be conducted in conjunction with a comprehensive training plan to prepare the applicant for an independent career as an academic physician-scientist. Training includes rigorous mentorship in scientific skills from a highly qualified sponsor, Dr. Jason Cyster; technical education from postdoctoral fellows in the applicant’s lab and collaborating labs; seminars, journal clubs, workshops, and conferences; and clinically geared activities. Research and training will take place at the University of California, San Francisco, which offers a highly innovative and collaborative immunology research environment and an exceptional medical school for clinical training.