Determination of CD91 Intracellular Signaling Pathway Following HSP Stimulation

Abstract Cancer immunosurveillance is dependent on the heat shock protein (HSP) receptor, CD91, which is expressed on professional antigen-presenting cells (APCs). While CD91-facilitated cross-presentation of HSP-chaperoned peptides has been well studied, CD91-mediated signaling is not completely defined. The binding of CD91 by immunogenic HSPs leads to production of unique inflammatory cytokine profiles by APCs. This requires the phosphorylation of tyrosine residues on intracellular domains of CD91 and activation of NF-κB. However, adaptor proteins associated with CD91 and molecules involved in signal transmission have not been characterized and their role in cancer immunosurveillance remains untested. Our general strategy to identify adaptor proteins involves crosslinking and co-immunoprecipitation of CD91 and its associated signaling complex following stimulation of CD91 with the immunogenic HSPs gp96, calreticulin, and hsp70. Preliminary studies with gp96 have identified Shc as an adaptor protein and AXL receptor tyrosine kinase and tyrosine-protein kinase Fgr as membrane associated kinases. The impact on their inhibition on cytokine release by APCs is being tested. We have also developed a novel mouse expressing mutant, non-signaling CD91, and its impact on cancer immunosurveillance will be determined. Investigation of these complexes will aid in understanding the signaling pathway that activates production of cytokine profiles within APCs. This project will allow us understand the pathways to priming immune responses responsible for cancer immunosurveillance and also to develop better therapeutic strategies for cancer and autoimmune diseases. Supported by grants from NIH (RO1 CA233803)