A Natural Hepatocyte Growth Factor/Scatter Factor Autocrine Loop in Myoblast Cells and the Effect of the Constitutive Met Kinase Activation on Myogenic Differentiation

• Published in: The Journal of cell biology Vol. 137; no. 5; pp. 1057 - 1068
• Main Authors: Anastasi, Sergio, Giordano, Silvia, Sthandier, Olga, Gambarotta, Giovanna, Maione, Rossella, Comoglio, Paolo, Amati, Paolo
• Format: Journal Article
• Language: English
• Published: United States Rockefeller University Press 02-06-1997; The Rockefeller University Press
• Subjects: Animals; Cell Differentiation - physiology; Cell growth; Cell lines; Cells; Cellular biology; Cellular differentiation; Dogs; Down-Regulation - physiology; Enzyme Activation; Epithelial cells; Gene Expression - physiology; Genes; Glyceraldehyde-3-Phosphate Dehydrogenases - genetics; Glyceraldehyde-3-Phosphate Dehydrogenases - metabolism; Hep G2 cells; Hepatocyte Growth Factor - pharmacology; Hepatocytes; Humans; Kidney Tubules, Distal - cytology; Liver; Liver - cytology; Mice; Mice, Inbred C3H; Muscles - chemistry; Muscles - cytology; Muscles - enzymology; Myoblasts; MyoD Protein - genetics; MyoD Protein - metabolism; Myogenin - genetics; Myogenin - metabolism; Phosphotransferases - metabolism; Proto-Oncogene Mas; Proto-Oncogene Proteins c-met; Receptor Protein-Tyrosine Kinases - genetics; Receptor Protein-Tyrosine Kinases - metabolism; Receptors; Recombinant Proteins - genetics; Recombinant Proteins - metabolism; RNA, Messenger - metabolism; Species Specificity; Teratocarcinoma; Transfection; Tumor Cells, Cultured - drug effects; Tumor Cells, Cultured - enzymology
• ISSN: 0021-9525; 1540-8140
• DOI: 10.1083/jcb.137.5.1057

As a rule, hepatocyte growth factor/scatter factor (HGF/SF) is produced by mesenchymal cells, while its receptor, the tyrosine kinase encoded by the met proto-oncogene, is expressed by the neighboring epithelial cells in a canonical paracrine fashion. In the present work we show that both HGF/SF and met are coexpressed by undifferentiated C2 mouse myoblasts. In growing cells, the autocrine loop is active as the receptor exhibits a constitutive phosphorylation on tyrosine that can be abrogated by exogenously added anti-HGF/SF neutralizing antibodies. The transcription of HGF/SF and met genes is downregulated when myoblasts stop proliferating and differentiate. The coexpression of HGF/SF and met genes is not exclusive to C2 cells since it has been assessed also in other myogenic cell lines and in mouse primary satellite cells, suggesting that HGF/SF could play a role in muscle development through an autocrine way. To analyze the biological effects of HGF/SF receptor activation, we stably expressed the constitutively activated receptor catalytic domain (p65tpr-met) in C2 cells. This active kinase determined profound changes in cell shape and inhibited myogenesis at both morphological and biochemical levels. Notably, a complete absence of muscle regulatory markers such as MyoD and myogenin was observed in p65tpr-met highly expressing C2 clones. We also studied the effects of the ectopic expression of human isoforms of met receptor (h-met) and of HGF/SF (h-HGF/SF) in stable transfected C2 cells. Single constitutive expression of h-met or h-HGF/SF does not alter substantially the growth and differentiation properties of the myoblast cells, probably because of a species-specific ligand-receptor interaction. A C2 clone expressing simultaneously both h-met and h-HGF/SF is able to grow in soft agar and shows a decrease in myogenic potential comparable to that promoted by p65tpr-met kinase. These data indicate that a met kinase signal released from differentiation-dependent control provides a negative stimulus for the onset of myogenic differentiation.