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

Clinical and Biological Perspectives on Noncanonical Esophageal Squamous Cell Carcinoma in Rare Subtypes

Esophageal squamous cell carcinoma (ESCC) remains the most common malignancy of the esophagus worldwide. Environmental and lifestyle exposures such as alcohol and tobacco have been well defined in the pathogenesis of ESCC, acting in concert with cell intrinsic epigenomic, genomic and transcriptomic changes. However, a variety of nonenvironmental etiologies including Fanconi anemia, lichen planus, chronic mucocutaneous candidiasis, esophageal epidermoid metaplasia, epidermolysis bullosa, tylosis, esophageal atresia, and achalasia receive minimal attention despite a high risk of ESCC in these diseases. The goal of this review was to promote clinical recognition and suggest a diagnostic framework for earlier detection of ESCC in patients with these rare diseases. In all the discussed conditions, a change in symptoms should trigger a prompt endoscopic evaluation, and endoscopic surveillance programs with advanced imaging techniques and chromoendoscopy should be considered. Moreover, we leverage the convergence of these diseases on ESCC to identify common mechanisms underlying malignant transformation including aberrant proliferation, mucosal barrier dysfunction, increased inflammation, and genome instability. In this study, we summarize the clinical presentation, pathologic findings, potential screening strategies, and common mechanisms of malignant transformation associated with these rare diseases that drive ESCC.

Role of iRhom2 in Olfaction: Implications for Odorant Receptor Regulation and Activity-Dependent Adaptation

The cell surface metalloprotease ADAM17 (a disintegrin and metalloprotease 17) and its binding partners iRhom2 and iRhom1 (inactive Rhomboid-like proteins 1 and 2) modulate cell-cell interactions by mediating the release of membrane proteins such as TNFα (Tumor necrosis factor α) and EGFR (Epidermal growth factor receptor) ligands from the cell surface. Most cell types express both iRhoms, though myeloid cells exclusively express iRhom2, and iRhom1 is the main iRhom in the mouse brain. Here, we report that iRhom2 is uniquely expressed in olfactory sensory neurons (OSNs), highly specialized cells expressing one olfactory receptor (OR) from a repertoire of more than a thousand OR genes in mice. iRhom2-/- mice had no evident morphological defects in the olfactory epithelium (OE), yet RNAseq analysis revealed differential expression of a small subset of ORs. Notably, while the majority of ORs remain unaffected in iRhom2-/- OE, OSNs expressing ORs that are enriched in iRhom2-/- OE showed fewer gene expression changes upon odor environmental changes than the majority of OSNs. Moreover, we discovered an inverse correlation between the expression of iRhom2 compared to OSN activity genes and that odor exposure negatively regulates iRhom2 expression. Given that ORs are specialized G-protein coupled receptors (GPCRs) and many GPCRs activate iRhom2/ADAM17, we investigated if ORs could activate iRhom2/ADAM17. Activation of an olfactory receptor that is ectopically expressed in keratinocytes (OR2AT4) by its agonist Sandalore leads to ERK1/2 phosphorylation, likely via an iRhom2/ADAM17-dependent pathway. Taken together, these findings point to a mechanism by which odor stimulation of OSNs activates iRhom2/ADAM17 catalytic activity, resulting in downstream transcriptional changes to the OR repertoire and activity genes, and driving a negative feedback loop to downregulate iRhom2 expression.

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

The protease ADAM17 plays an important role in inflammation and cancer and is regulated by iRhom2. Mutations in the cytosolic N-terminus of human iRhom2 cause tylosis with oesophageal cancer (TOC). In mice, partial deletion of the N-terminus results in a curly hair phenotype (cub). These pathological consequences are consistent with our findings that iRhom2 is highly expressed in keratinocytes and in oesophageal cancer. Cub and TOC are associated with hyperactivation of ADAM17-dependent EGFR signalling. However, the underlying molecular mechanisms are not understood. We have identified a non-canonical, phosphorylation-independent 14-3-3 interaction site that encompasses all known TOC mutations. Disruption of this site dysregulates ADAM17 activity. The larger cub deletion also includes the TOC site and thus also dysregulated ADAM17 activity. The cub deletion, but not the TOC mutation, also causes severe reductions in stimulated shedding, binding, and stability of ADAM17, demonstrating the presence of additional regulatory sites in the N-terminus of iRhom2. Overall, this study contrasts the TOC and cub mutations, illustrates their different molecular consequences, and reveals important key functions of the iRhom2 N-terminus in regulating ADAM17.