The multifunctional post-proline dipeptidyl peptidase, DPP9, in mice, cell biology and immunity

Abstract

Dipeptidyl peptidase 9 (DPP9) is a ubiquitous intracellular post-proline protease of the DPP4 (S9b) family of atypical serine proteases. Emerging data support roles for DPP9 in intracellular signalling, particularly in the epidermal growth factor receptor pathway, in immune cells, particularly in macrophages and antigen processing, and in energy metabolism. The focus of this review is the roles of DPP9 in regulating physiological and cellular processes. Such data is derived from a genetically modified mouse strain and from manipulations of cell lines. The mouse strain that lacks DPP9 enzyme activity is homozygous lethal. DPP9 alters behaviours, such as cell adhesion, of cancer cell lines. This review points to the functional importance of DPP9 in immunity, metabolism and cancer.