ALK1 regulates the internalization of endoglin and the type III TGF-ß receptor.

Complex formation and endocytosis of transforming growth factor-ß (TGF-ß) receptors play important roles in signaling. However, their interdependence remained unexplored. Here, we demonstrate that ALK1, a TGF-ß type I receptor prevalent in endothelial cells, forms stable complexes at the cell surface with endoglin and with type III TGF-ß receptors (TßRIII). We show that ALK1 undergoes clathrin-mediated endocytosis (CME) faster than ALK5, type II TGF-ß receptor (TßRII), endoglin, or TßRIII. These complexes regulate the endocytosis of the TGF-ß receptors, with a major effect mediated by ALK1. Thus, ALK1 enhances the endocytosis of TßRIII and endoglin, while ALK5 and TßRII mildly enhance endoglin, but not TßRIII, internalization. Conversely, the slowly endocytosed endoglin has no effect on the endocytosis of either ALK1, ALK5, or TßRII, while TßRIII has a differential effect, slowing the internalization of ALK5 and TßRII, but not ALK1. Such effects may be relevant to signaling, as BMP9-mediated Smad1/5/8 phosphorylation is inhibited by CME blockade in endothelial cells. We propose a model that links TGF-ß receptor oligomerization and endocytosis, based on which endocytosis signals are exposed/functional in specific receptor complexes. This has broad implications for signaling, implying that complex formation among various receptors regulates their surface levels and signaling intensities.

Awareness of family health history in a predominantly young adult population.

Family health history (FHH) is a key predictor of health risk and is universally important in preventive care. However, patients may not be aware of the importance of FHH, and thus, may fail to accurately or completely share FHH with health providers, thereby limiting its utility. In this study, we conducted an online survey of 294 young adults and employees based at a US university setting regarding their knowledge, sharing behaviors, and perceived importance of FHH, and use of electronic clinical tools to document and update FHH. We also evaluated two educational interventions (written and video) to promote knowledge about FHH and its importance to health. We found that 93% of respondents were highly aware of their FHH, though only 39% reported collecting it and 4% using an online FHH tool. Seventy-three percent of respondents, particularly women, had shared FHH with their doctor when prompted, and fewer had shared it with family members. Participants in the video group were significantly more likely to understand the benefits of FHH than those in the written group (p = 0.02). In summary, educational resources, either video or written, will be helpful to promote FHH collection, sharing, and use of online FHH tools.

Increased type III TGF-ß receptor shedding decreases tumorigenesis through induction of epithelial-to-mesenchymal transition.

The type III TGF-ß receptor (TßRIII) is a TGF-ß co-receptor that presents ligand to the type II TGF-ß receptor to initiate signaling. TßRIII also undergoes ectodomain shedding to release a soluble form (sTßRIII) that can bind ligand, sequestering it away from cell surface receptors. We have previously identified a TßRIII extracellular mutant that has enhanced ectodomain shedding ("super shedding (SS)"-TßRIII-SS). Here, we utilize TßRIII-SS to study the balance of cell surface and soluble TßRIII in the context of lung cancer. We demonstrate that expressing TßRIII-SS in lung cancer cell models induces epithelial-to-mesenchymal transition (EMT) and that these TßRIII-SS (EMT) cells are less migratory, invasive and adhesive and more resistant to gemcitabine. Moreover, TßRIII-SS (EMT) cells exhibit decreased tumorigenicity but increased growth rate in vitro and in vivo. These studies suggest that the balance of cell surface and soluble TßRIII may regulate a dichotomous role for TßRIII during cancer progression.