Cell-type specific regulation of myostatin signaling.
The transforming growth factor (TGF)-β family member myostatin is an important regulator of myoblast, adipocyte, and fibroblast growth and differentiation, but the signaling mechanisms remain to be established. We therefore determined the contribution of myostatin type I receptors activin receptor-like kinase-4 (ALK4) and -5 (ALK5) and different coreceptors in C2C12 myoblasts, C3H10T1/2 mesenchymal stem cells, and 3T3-L1 fibroblasts, as well as in primary myoblast and fibroblasts. We performed siRNA-mediated knockdown of each receptor and measured signaling activity using Smad3-dependent luciferase and Smad2 phosphorylation assays with nontargeting siRNA as control. We find that myostatin utilizes ALK4 in myoblasts, whereas it has a preference for ALK5 in nonmyogenic cells. Notably, our results show that coreceptor Cripto is expressed in myoblasts but not in the nonmyogenic cells and that it regulates myostatin activity. More specifically, myostatin requires Cripto in myoblasts, whereas Cripto represses activin activity and TGF-β signaling is Cripto independent. Cripto-mediated myostatin signaling is dependent on both epidermal growth factor (EGF)-like and Cripto-FRL1-cryptic (CFC) domains, whereas activin signaling is solely conferred by the CFC domain. Furthermore, Cripto down-regulation enhances myoblast differentiation, showing its importance in myostatin signaling. Together, our results identify a molecular mechanism that explains the cell-type specific aspects of signaling by myostatin and other TGF-β family members.
Center for Human and Clinical Genetics, Leiden University Medical Center, Postzone S4-P, PO Box 9600, 2300RC, Leiden, The Netherlands.
Dwi U
DU
Kemaladewi
David J J
DJ
de Gorter
Annemieke
A
Aartsma-Rus
Gert-Jan
GJ
van Ommen
Peter
P
ten Dijke
Peter A C
PA
't Hoen
Willem M
WM
Hoogaars
D029404:Activin Receptors / Q000378:metabolism; D030201:Activin Receptors, Type I / Q000235:genetics / Q000378:metabolism*; D028341:Activins / Q000378:metabolism; D000818:Animals; D002454:Cell Differentiation / Q000502:physiology; D002460:Cell Line; D004815:Epidermal Growth Factor / Q000235:genetics / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology*; D006801:Humans; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D032446:Myoblasts / Q000166:cytology / Q000502:physiology*; D055435:Myostatin / Q000378:metabolism*; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D000077293:Receptor, Transforming Growth Factor-beta Type I; D018125:Receptors, Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D016212:Transforming Growth Factor beta / Q000378:metabolism
D008562:Membrane Glycoproteins; D055435:Myostatin; D009363:Neoplasm Proteins; D034741:RNA, Small Interfering; D018125:Receptors, Transforming Growth Factor beta; C489450:Tdgf1 protein, mouse; D016212:Transforming Growth Factor beta; D028341:Activins; D004815:Epidermal Growth Factor; D017346:Protein Serine-Threonine Kinases; D029404:Activin Receptors; D030201:Activin Receptors, Type I; C498933:Acvr1b protein, mouse; D000077293:Receptor, Transforming Growth Factor-beta Type I; C000625841:TGFBR1 protein, human; C000625842:Tgfbr1 protein, mouse