Effects of RACK1 on cell migration and IGF-I signalling in cardiomyoctes are not dependent on an association with the IGF-IR.
RACK1 can act as a scaffolding protein to integrate IGF-IR and integrin signalling in transformed cells but its actions in regulating IGF-IR signalling in non-transformed cells are less well understood. Here, we investigated the function of RACK1 in the non-transformed cardiomyocyte cell line H9c2. Overexpression of RACK1 in H9c2 cells was sufficient to increase cell size, increase adhesion to collagen 1, enhance protection from hydrogen peroxide-induced cell death, and increase cell migration. However, cell proliferation was decreased in these cells. Small interfering RNA (siRNA)-mediated suppression of RACK1 in H9c2 cells resulted in decreased cell adhesion and migration, but had no effect on cell proliferation or size. Increased basal and IGF-I-mediated Erk phosphorylation was observed in RACK1-overexpressing H9c2 cells. Interestingly, contrary to observations in transformed cells, RACK1 was not observed to interact with the IGF-IR in H9c2 cells. Also in contrast to observations in transformed cells, IGF-I promoted recruitment of Src to RACK1 as well as recruitment of PKCalpha, and PKCepsilon to RACK1. Overall, the data indicate that in H9c2 cells RACK1 can influence cell size, cell survival, adhesion, migration, but its responses to IGF-I are independent of an association with the IGF-IR. Thus, the composition of the RACK1 scaffolding complex and its effects on IGF-I signalling may be different in transformed and non-transformed cells.
O'Donovan
Helen C
HC
Cell Biology Laboratory, Department of Biochemistry, BioSciences Institute, National University of Ireland, Cork, Ireland.
Kiely
Patrick A
PA
O'Connor
Rosemary
R
D000818:Animals; D002448:Cell Adhesion; D016923:Cell Death; D002460:Cell Line; D002465:Cell Movement; D049109:Cell Proliferation; D048429:Cell Size; D024042:Collagen Type I / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D046912:Multiprotein Complexes / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000201:enzymology / Q000378:metabolism*; D010766:Phosphorylation; D051571:Protein Kinase C-alpha / Q000378:metabolism; D051744:Protein Kinase C-epsilon / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering; D051381:Rats; D017526:Receptor, IGF Type 1 / Q000378:metabolism*; D000075370:Receptors for Activated C Kinase; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D014162:Transfection; D019061:src-Family Kinases / Q000378:metabolism
D024042:Collagen Type I; D046912:Multiprotein Complexes; D034741:RNA, Small Interfering; D000075370:Receptors for Activated C Kinase; D011956:Receptors, Cell Surface; D007334:Insulin-Like Growth Factor I; D006861:Hydrogen Peroxide; D017526:Receptor, IGF Type 1; D019061:src-Family Kinases; D051571:Protein Kinase C-alpha; D051744:Protein Kinase C-epsilon; D048049:Extracellular Signal-Regulated MAP Kinases