The Asn418-linked N-glycan of ErbB3 plays a crucial role in preventing spontaneous heterodimerization and tumor promotion.
ErbB2 and ErbB3, two members of the ErbB family, form a high-affinity heregulin coreceptor that elicits potent mitogenic and transforming signals, and clinical studies indicate that these receptors play an important role in tumor incidence and progression. To determine whether N-glycosylation is involved in the function of ErbB3, a series of human ErbB3 molecules devoid of N-glycans were prepared and transfected to Flp-In-CHO cells for stable expression. A cross-linking study showed that the Asn(418) to Gln mutant (N418Q) of ErbB3 underwent autodimerization without its ligand, heregulin. The wild-type or N418Q mutant of ErbB3 was next coexpressed with ErbB2 in Flp-In-CHO cells, and the effect of N-glycan on heterodimerization was examined. The N418Q mutant of ErbB3 was autodimerized with ErbB2 without ligand stimulation, and receptor tyrosine phosphorylation and subsequent extracellular signal-regulated kinase (ERK) and Akt phosphorylation were promoted in the absence of heregulin. A cell proliferation assay and a soft agar colony formation assay showed that the N418Q mutant of ErbB3 coexpressed with ErbB2 promoted cell proliferation and colony formation in soft agar in an ERK- and Akt-dependent manner. The mutation also promoted the growth of tumors in athymic mice when injected s.c. These findings suggest that the Asn(418)-linked N-glycan in ErbB3 plays an essential role in regulating receptor heterodimerization with ErbB2 and might have an effect on transforming activity.
Yokoe
Shunichi
S
Department of Biochemistry, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan.
Takahashi
Motoko
M
Asahi
Michio
M
Lee
Seung Ho
SH
Li
Wei
W
Osumi
Daisuke
D
Miyoshi
Eiji
E
Taniguchi
Naoyuki
N
D000818:Animals; D001216:Asparagine; D020134:Catalytic Domain / Q000502:physiology; D049109:Cell Proliferation; D002471:Cell Transformation, Neoplastic; D002478:Cells, Cultured; D019281:Dimerization; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005260:Female; D006031:Glycosylation; D051379:Mice; D008819:Mice, Nude; D050505:Mutant Proteins / Q000502:physiology; D020890:Neuregulin-1 / Q000494:pharmacology; D011499:Protein Processing, Post-Translational / Q000502:physiology*; D020893:Receptor, ErbB-3 / Q000737:chemistry* / Q000378:metabolism*; D014162:Transfection
D050505:Mutant Proteins; D020890:Neuregulin-1; D001216:Asparagine; D020893:Receptor, ErbB-3; D048049:Extracellular Signal-Regulated MAP Kinases