Mutations in the adaptor protein PSTPIP1 cause a spectrum of autoinflammatory diseases, including PAPA and PAMI; however, the mechanism underlying these diseases remains unknown. Most of these mutations lie in PSTPIP1 F-BAR domain, which binds to LYP, a protein tyrosine phosphatase associated with arthritis and lupus. To shed light on the mechanism by which these mutations generate autoinflammatory disorders, we solved the structure of the F-BAR domain of PSTPIP1 alone and bound to the C-terminal homology segment of LYP, revealing a novel mechanism of recognition of Pro-rich motifs by proteins in which a single LYP molecule binds to the PSTPIP1 F-BAR dimer. The residues R228, D246, E250, and E257 of PSTPIP1 that are mutated in immunological diseases directly interact with LYP. These findings link the disruption of the PSTPIP1/LYP interaction to these diseases, and support a critical role for LYP phosphatase in their pathogenesis.
This work has been funded by Programa de Apoyo a Planes Estratégicos de Investigación de Estructuras de Investigación de Excelencia co-funded by Junta de Castilla y León and ERDF CLC-2017-01 (JMdeP), Programa Estratégico Instituto de Biología y Genética Molecular (IBGM), Junta de Castilla y León CCVC8485 (AA), Fundación Ramón Areces (AA) and Consejería de Sanidad de la Junta de Castilla y León (AA).