The hyaluronan receptor RHAMM regulates extracellular-regulated kinase.
We have identified two RHAMM (receptor for hyaluronan-mediated motility) isoforms that encode an alternatively spliced exon 4 (Hall, C. L., Yang, B., Yang, X., Zhang, S., Turley, M., Samuel, S., Lange, L. A., Wang, C., Curpen, G. D., Savani, R. C., Greenberg, A. H., and Turley, E. A. (1995) Cell 82, 19-26 and Wang, C., Entwistle, J., Hou, G., Li, Q., and Turley, E. A. (1996) Gene 174, 299-306). One of these, RHAMM variant 4 (RHAMMv4), is transforming when overexpressed and regulates Ras signaling (Hall et al.). Here we note using flow cytometry and confocal analysis that RHAMM isoforms encoding exon 4 occur both on the cell surface and in the cytoplasm. Epitope-tagging experiments indicate that RHAMMv4 occurs only in the cytoplasm. Several observations suggest that both cell surface RHAMM isoforms and RHAMMv4 are involved in regulating extracellular-regulated kinase (ERK) activity. Affinity-purified anti-RHAMM exon 4 antibodies block the ability of platelet-derived growth factor to activate ERK, and these reagents modify the protein tyrosine phosphorylation profile of proteins resulting from treatment with platelet-derived growth factor. A dominant negative form of RHAMMv4 inhibits mutant active Ras activation of ERK and coimmunoprecipitates with both mitogen-activated protein kinase kinase and ERK, suggesting that the intracellular RHAMMv4 acts downstream of Ras, possibly at the level of mitogen-activated protein kinase kinase-ERK interactions. Consistent with this, overexpression of RHAMMv4 constitutively activates ERK. These results identify a novel mechanism for the regulation of the Ras-ERK signaling pathway and suggest that RHAMM plays multiple roles in this regulation.
Zhang
S
S
Hospital for Sick Children, Division of Cardiovascular Research, Toronto, Ontario, Canada M5G1X8.
Chang
M C
MC
Zylka
D
D
Turley
S
S
Harrison
R
R
Turley
E A
EA
D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002460:Cell Line; D004789:Enzyme Activation; D005091:Exons; D016326:Extracellular Matrix Proteins / Q000235:genetics / Q000378:metabolism*; D018960:Hyaluronan Receptors / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D009154:Mutation; D018631:ras Proteins / Q000378:metabolism
D016326:Extracellular Matrix Proteins; D018960:Hyaluronan Receptors; C098946:hyaluronan-mediated motility receptor; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D018631:ras Proteins