| First Author | He Q | Year | 2017 |
| Journal | Proc Natl Acad Sci U S A | Volume | 114 |
| Issue | 45 | Pages | E9559-E9568 |
| PubMed ID | 29078380 | Mgi Jnum | J:257220 |
| Mgi Id | MGI:6101032 | Doi | 10.1073/pnas.1712670114 |
| Citation | He Q, et al. (2017) Large G protein alpha-subunit XLalphas limits clathrin-mediated endocytosis and regulates tissue iron levels in vivo. Proc Natl Acad Sci U S A 114(45):E9559-E9568 |
| abstractText | Alterations in the activity/levels of the extralarge G protein alpha-subunit (XLalphas) are implicated in various human disorders, such as perinatal growth retardation. Encoded by GNAS, XLalphas is partly identical to the alpha-subunit of the stimulatory G protein (Gsalpha), but the cellular actions of XLalphas remain poorly defined. Following an initial proteomic screen, we identified sorting nexin-9 (SNX9) and dynamins, key components of clathrin-mediated endocytosis, as binding partners of XLalphas. Overexpression of XLalphas in HEK293 cells inhibited internalization of transferrin, a process that depends on clathrin-mediated endocytosis, while its ablation by CRISPR/Cas9 in an osteocyte-like cell line (Ocy454) enhanced it. Similarly, primary cardiomyocytes derived from XLalphas knockout (XLKO) pups showed enhanced transferrin internalization. Early postnatal XLKO mice showed a significantly higher degree of cardiac iron uptake than wild-type littermates following iron dextran injection. In XLKO neonates, iron and ferritin levels were elevated in heart and skeletal muscle, where XLalphas is normally expressed abundantly. XLKO heart and skeletal muscle, as well as XLKO Ocy454 cells, showed elevated SNX9 protein levels, and siRNA-mediated knockdown of SNX9 in XLKO Ocy454 cells prevented enhanced transferrin internalization. In transfected cells, XLalphas also inhibited internalization of the parathyroid hormone and type 2 vasopressin receptors. Internalization of transferrin and these G protein-coupled receptors was also inhibited in cells expressing an XLalphas mutant missing the Galpha portion, but not Gsalpha or an N-terminally truncated XLalphas mutant unable to interact with SNX9 or dynamin. Thus, XLalphas restricts clathrin-mediated endocytosis and plays a critical role in iron/transferrin uptake in vivo. |
