Fly DPP10 acts as a channel ancillary subunit and possesses peptidase activity

Abstract

Mammalian DPP6 (DPPX) and DPP10 (DPPY) belong to a family of dipeptidyl peptidases, but lack enzyme activity. Instead, these proteins form complexes with voltage-gated K+ channels in Kv4 family to control their gating and other properties. Here, we find that the fly DPP10 ortholog acts as an ancillary subunit of Kv4 channels and digests peptides. Similarly to mammalian DPP10, the fly ortholog tightly binds to rat Kv4.3 protein. The association causes negative shifts in voltage dependence of channel activation and steady state inactivation. It also results in faster inactivation and recovery from inactivation. In addition to its channel regulatory role, fly DPP10 exhibits significant dipeptidyl peptidase activity with Gly-Pro-MCA (glycyl-L-proline 4-methylcoumaryl-7-amide) as a substrate. Heterologously expressed Flag-tagged fly DPP10 and human DPP4 show similar Km values towards this substrate. However, fly DPP10 exhibits approximately a 6-times-lower relative kcat value normalized with anti-Flag immunoreactivity than human DPP4. These results demonstrate that fly DPP10 is a dual functional protein, controlling Kv4 channel gating and removing bioactive peptides.

Manipulation of dipeptidylpeptidase 10 in mouse and human in vivo and in vitro models indicates a protective role in asthma

“…DPP10 is a potassium channel-associated protein ( Chen et al, 2014 ; Kitazawa et al, 2015 ), but unlike other DPP family members, mammalian DPP10 lacks enzymatic activity and is unable to cleave terminal dipeptides from asthma-related cytokines and chemokines ( Allen et al, 2003 ). Interestingly, however, in Drosophila , DPP10 both acts as an ion channel substrate and has peptidase activity ( Shiina et al, 2016 ).…”

Drosophila as a Rapid Screening Model to Evaluate the Hypoglycemic Effects of Dipeptidyl Peptidase 4 (DPP4) Inhibitors: High Evolutionary Conservation of DPP4

“…Before this study, DPP4 activity had been previously documented in Drosophila [28,29] and here, we demonstrate that this protein occupies an evolutionary position intermediate to the DPP4s found in vertebrates and fungi. Other insect DPP4 appear to be in the same evolutionary locality [39]. It is noteworthy that the DPP4 protein shows a substantial level of sequence identity, approximately 70%, between the different species, particularly the domains associated with exopeptidase activity (Figures 1 and S1).…”

“…As a general principle, the greater the number of species included in a conservation analysis, the greater its robustness [41]. In our study, we adopted this perspective by including data from 47 different species, making it more comprehensive than a previous study on DPP10, which focused on a smaller set of species [39]. The resulting phylogenetic analysis revealed a gradual transformation consistent with evolutionary patterns, ranging from fungi to mammals (Figure 2).…”

“…Human CD26/dipeptidyl peptidase 4 (DPP4) is a membrane-bound glycoprotein consisting of 766 amino acids and comprising four distinct regions: an N-terminal short cytoplasmic domain (residues 1-6), a transmembrane domain (residues 7-28), a flexible region (residues [29][30][31][32][33][34][35][36][37][38][39], and a C-terminal extracellular domain (residues 40-766) containing peptidase activity [1]. This protein is found in many types of cells in the body, and a circulating soluble form can also be found [2].…”