Analysis of the function of ADAM17 in iRhom2 curly-bare and tylosis with esophageal cancer mutant mice

Abstract

Tylosis with Oesophageal Cancer (TOC), is a rare familial disorder caused by cytoplasmic mutations in inactive rhomboid 2 (iR2). iR2 and the related iR1 are key regulators of the membrane-anchored metalloprotease ADAM17, which is required for activating EGFR ligands and for releasing pro-inflammatory cytokines such as TNFa. A cytoplasmic deletion in iR2, including the TOC site, leads to curly whiskers and bare skin (cub) in mice, whereas a knock-in TOC mutation causes less severe alopecia and wavy fur. The abnormal skin and hair phenotypes of iR2cub/cub and iR2toc/toc mice depend on amphiregulin and ADAM17, since loss of one allele of either gene rescues the fur phenotypes. Remarkably, iR1-/-iR2cub/cub mice survive, despite a lack of mature ADAM17, whereas iR2cub/cubAdam17-/-mice die perinatally, suggesting that the iR2cub gain-of-function mutation requires the presence of ADAM17, but not its catalytic activity. iR2toc does not substantially reduce the levels of mature ADAM17, but instead affects its function in a substrate selective manner. Our findings provide new insights into the role of the cytoplasmic domain of iR2 in vivo, with implications for the treatment of TOC patients.

Pathological mutations reveal the key role of the cytosolic iRhom2 N-terminus for phosphorylation-independent 14-3-3 interaction and ADAM17 binding, stability, and activity

“…Our findings that cub and TOC mutations decreases levels of mature ADAM17 is in line with recent in vivo and ex vivo results (Siggs et al, 2014, Rabinowitsch et al, 2023). However, these findings are counterintuitive to the earlier reported elevated ADAM17 shedding activity (Brooke et al, 2014, Hosur et al, 2017, Hosur et al, 2018a, Hosur et al, 2018b).…”

“…The N-terminus of iRhoms emerges as a critical determinant for the stability and activity of the iRhom-ADAM17 complex. This is again supported by our data and was recently also confirmed in vivo : mice with the cub mutation show decreased ADAM17 levels in different tissues (Rabinowitsch et al, 2023). Recent findings highlight the significance of FRMD8-binding in regulating iRhom stability and, consequently, ADAM17 stability and functions (Künzel et al, 2018, Oikonomidi et al, 2018).…”

“…It is important to note that our study did not explore the integration of these mechanisms into a more complex in vivo system. Importantly, ADAM17 activity at the cellular level in vivo is dependent on cell type-specific endogenous protein levels of iRhom1, iRhom2 and ADAM17, which will also influence the manifestations of pathological changes in the iRhom-ADAM17 axis (Rabinowitsch et al, 2023). Here it is also important to consider that ADAM17 substrate specificity appears to be differentially regulated by iRhom1 and iRhom2 (Maretzky et al, 2013, Tang et al, 2020).…”

Pathological mutations reveal the key role of the cytosolic iRhom2 N-terminus for phosphorylation-independent 14-3-3 interaction and ADAM17 binding, stability, and activity

“…Our findings that cub and TOC mutations decrease levels of matured ADAM17 are in line with recent in vivo and ex vivo results [ 84 , 100 ]. However, these findings are counterintuitive to the earlier reported elevated ADAM17 shedding activity [ 14 , 39 , 40 , 42 ].…”

“…In contrast, expression of the murine iRhom2 cub deletion does not promote higher levels of matured ADAM17 (Fig. 3 A), which is in line with recent in vivo findings [ 84 ]. Furthermore, the three deletions nd197, nd349 and nd370 showed also a significant decrease in matured ADAM17 levels compared to wt-iRhom2 (Fig.…”