Specific binding of GLP-2 to the GLP-1R
The binding to the mGLP-1R combined with the low, but specific binding to the hGLP-1R, inspired us to further characterize the action of hGLP-2 in the hGLP-1R system using the same experimental setup as for the hGLP-2R (figure 1). The two full-length variants hGLP-2(1-33) and hGLP-2(1-33,M10Y) both showed weak agonistic properties on the hGLP-1R with >1000-fold lower potency compared to endogenous GLP-1 (figure 6a and table 1). These data corresponds to previous data (Gasbjerg et al. 2018). In contrast, the two N-terminally truncated variants hGLP-2(3-33) and hGLP-2(3-33,M10Y) did not activate the hGLP-1R (figure 6b and table 1). To confirm that the hGLP-2 mediated cAMP response was mediated through the GLP-1R, we reversed the signal by employing the high affinity GLP-1R antagonist exendin(9-39) (Schirra et al. 1998). A rightward shift was observed for the dose-response curve of hGLP-2(1-33) in the presence of exendin(9-39) (figure 6c and table 1), demonstrating that the cAMP accumulation induced by hGLP-2(1-33) is mediated through the hGLP-1R, in a similar manner, as that of GLP-1. In contrast, increasing concentrations (up to 1 µM) of hGLP-2(3-33,M10Y) did not affect the activity of GLP-1 on the hGLP-1R (figure 6d and table 1).‬‬‬‬‬‬