A disintegrin and metalloprotease 10 (ADAM10) is a ubiquitously expressed transmembrane metalloprotease that cleaves the extracellular regions from its transmembrane substrates. ADAM10 is essential for embryonic development and is implicated in cancer, Alzheimer, and inflammatory diseases. The tetraspanins are a superfamily of 33 four-transmembrane proteins in mammals, of which the TspanC8 subgroup (Tspan5, 10, 14, 15, 17, and 33) promote ADAM10 intracellular trafficking and enzymatic maturation. However, the interaction between TspanC8s and ADAM10 has only been demonstrated in overexpression systems and the interaction mechanism remains undefined. To address these issues, an antibody was developed to Tspan14, which was used to show co-immunoprecipitation of Tspan14 with ADAM10 in primary human cells. Chimeric Tspan14 constructs demonstrated that the large extracellular loop of Tspan14 mediated its co-immunoprecipitation with ADAM10, and promoted ADAM10 maturation and trafficking to the cell surface. Chimeric ADAM10 constructs showed that membrane-proximal stalk, cysteine-rich, and disintegrin domains of ADAM10 mediated its co-immunoprecipitation with Tspan14 and other TspanC8s. This TspanC8-interacting region was required for ADAM10 exit from the endoplasmic reticulum. Truncated ADAM10 constructs revealed differential TspanC8 binding requirements for the stalk, cysteine-rich, and disintegrin domains. Moreover, Tspan15was the only TspanC8 to promote cleavage of the ADAM10 substrate N-cadherin, whereas Tspan14 was unique in reducing cleavage of the platelet collagen receptor GPVI. These findings suggest that ADAM10 may adopt distinct conformations in complex with different TspanC8s, which could impact on substrate selectivity. Furthermore, this study identifies regions of TspanC8s and ADAM10 for potential interaction-disrupting therapeutic targeting.

A disintegrin and metalloprotease (ADAM) 10 and ADAM17 are ubiquitous transmembrane “molecular scissors” which proteolytically cleave, or shed, the extracellular regions of other transmembrane proteins. ADAM10 is essential for development because it cleaves Notch proteins to induce Notch signaling and regulate cell fate decisions. ADAM17 is regarded as a first line of defense against injury and infection, by releasing tumor necrosis factor α (TNFα) to promote inflammation and epidermal growth factor (EGF) receptor ligands to maintain epidermal barrier function. However, the regulation of ADAM10 and ADAM17 trafficking and activation are not fully understood. This review will describe how the TspanC8 subgroup of tetraspanins (Tspan5, 10, 14, 15, 17, and 33) and the iRhom subgroup of protease-inactive rhomboids (iRhom1 and 2) have emerged as important regulators of ADAM10 and ADAM17, respectively. In particular, they are required for the enzymatic maturation and trafficking to the cell surface of the ADAMs, and there is evidence that different TspanC8s and iRhoms target the ADAMs to distinct substrates. The TspanC8s and iRhoms have not been studied functionally on platelets. On these cells, ADAM10 is the principal sheddase for the platelet collagen receptor GPVI, and the regulatory TspanC8s are Tspan14, 15, and 33, as determined from proteomic data. Platelet ADAM17 is the sheddase for the von Willebrand factor (vWF) receptor GPIb, and iRhom2 is the only iRhom that is expressed. Induced shedding of either GPVI or GPIb has therapeutic potential, since inhibition of either receptor is regarded as a promising anti-thrombotic therapy. Targeting of Tspan14, 15, or 33 to activate platelet ADAM10, or iRhom2 to activate ADAM17, may enable such an approach to be realized, without the toxic side effects of activating the ADAMs on every cell in the body.

and from several drug and device companies active in atrial fibrillation. PK has previously received honoraria from several such companies. PK and LF are listed as inventors on 2 patents held by the University of Birmingham ("Atrial fibrillation therapy," WO 2015140571; "Markers for atrial fibrillation," WO 2016012783).

Genome-wide association studies have uncovered over a 100 genetic loci associated with atrial fibrillation (AF), the most common arrhythmia. Many of the top AF-associated loci harbor key cardiac transcription factors, including PITX2, TBX5, PRRX1, and ZFHX3. Moreover, the vast majority of the AF-associated variants lie within noncoding regions of the genome where causal variants affect gene expression by altering the activity of transcription factors and the epigenetic state of chromatin. In this review, we discuss a transcriptional regulatory network model for AF defined by effector genes in Genome-wide association studies loci. We describe the current state of the field regarding the identification and function of AF-relevant gene regulatory networks, including variant regulatory elements, dose-sensitive transcription factor functionality, target genes, and epigenetic states. We illustrate how altered transcriptional networks may impact cardiomyocyte function and ionic currents that impact AF risk. Last, we identify the need for improved tools to identify and functionally test transcriptional components to define the links between genetic variation, epigenetic gene regulation, and atrial function.

The recruitment of blood leukocytes across the endothelium to sites of tissue infection is central to inflammation, but also promotes chronic inflammatory diseases. A disintegrin and metalloproteinase 10 (ADAM10) is a ubiquitous transmembrane molecular scissor that is implicated in leukocyte transmigration by proteolytically cleaving its endothelial substrates. These include VE-cadherin, a homotypic adhesion molecule that regulates endothelial barrier function, and transmembrane chemokines CX3CL1 and CXCL16, which have receptors on leukocytes. However, a definitive role for endothelial ADAM10 in transmigration of freshly isolated primary leukocytes under flow has not been demonstrated, and the relative importance of distinct ADAM10 substrates is unknown. Emerging evidence suggests that ADAM10 can be regarded as six different molecular scissors with different substrate specificities, depending on which of six TspanC8 tetraspanins it is associated with, but TspanC8s remain unstudied in leukocyte transmigration. In the current study, ADAM10 knockdown on primary HUVECs was found to impair transmigration of freshly isolated human peripheral blood T lymphocytes, but not neutrophils or B lymphocytes, in an in vitro flow assay. This impairment was due to delayed transmigration rather than a complete block, and was overcome in the presence of neutrophils. Transmigration of purified lymphocytes was dependent on ADAM10 regulation of VE-cadherin, but not CX3CL1 and CXCL16. Tspan5 and Tspan17, the two most closely related TspanC8s by sequence, were the only TspanC8s that regulated VE-cadherin expression and were required for lymphocyte transmigration. Therefore endothelial Tspan5- and Tspan17-ADAM10 complexes may regulate inflammation by maintaining normal VE-cadherin expression and promoting T lymphocyte transmigration.