Improvement of photoaffinity SPR imaging platform and determination of the binding site of p62/SQSTM1 to p38 MAP kinase.

p38 mitogen-activated protein kinase (MAPK) is a member of the serine/threonine kinases and is activated in response to stress stimuli, such as cytokines, ultraviolet irradiation, heat shock, and osmotic shock. We revealed in a previous report that p62/SQSTM1, known to participate in proteasomal or autophagosomal protein degradation and cytokine receptor signal transduction pathways, binds to p38 to regulate specifically. Herein, we describe the improvement of the photoaffinity-thiol linker of our SPR imaging platform, which enabled us to determine the binding site of p62 to p38. SPR imaging experiments using a new photoaffinity linker 2 to immobilize the peptides derived from p62 on gold substrate indicate that the domain comprising amino acids 164-190 of p62 binds to p38 directly. These SPR analysis data and empirical biologic data reveal that the binding site of p62 to p38 is the domain corresponding to 173-182.