Galectin-1 is a novel structural component and a major regulator of h-ras nanoclusters.
The organization of Ras proteins into nanoclusters on the inner plasma membrane is essential for Ras signal transduction, but the mechanisms that drive nanoclustering are unknown. Here we show that epidermal growth factor receptor activation stimulates the formation of H-Ras.GTP-Galectin-1 (Gal-1) complexes on the plasma membrane that are then assembled into transient nanoclusters. Gal-1 is therefore an integral structural component of the H-Ras-signaling nanocluster. Increasing Gal-1 levels increases the stability of H-Ras nanoclusters, leading to enhanced effector recruitment and signal output. Elements in the H-Ras C-terminal hypervariable region and an activated G-domain are required for H-Ras-Gal-1 interaction. Palmitoylation is not required for H-Ras-Gal-1 complex formation, but is required to anchor H-Ras-Gal-1 complexes to the plasma membrane. Our data suggest a mechanism for H-Ras nanoclustering that involves a dual role for Gal-1 as a critical scaffolding protein and a molecular chaperone that contributes to H-Ras trafficking by returning depalmitoylated H-Ras to the Golgi complex for repalmitoylation.
Belanis
Liron
L
Department of Neurobiochemistry, George S. Wise Faculty of Life Sciences, Tel Aviv University, 69978 Tel Aviv, Israel.
Plowman
Sarah J
SJ
Rotblat
Barak
B
Hancock
John F
JF
Kloog
Yoel
Y
D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D006224:Cricetinae; D004815:Epidermal Growth Factor / Q000494:pharmacology; D037483:Galectin 1 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006056:Golgi Apparatus / Q000378:metabolism; D006801:Humans; D054878:Lipoylation; D008958:Models, Molecular; D046912:Multiprotein Complexes; D053758:Nanoparticles; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D014162:Transfection; D018631:ras Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
D037483:Galectin 1; D046912:Multiprotein Complexes; D011993:Recombinant Fusion Proteins; D004815:Epidermal Growth Factor; D018631:ras Proteins