Structure of the Plexin Ectodomain Bound by Semaphorin-Mimicking Antibodies.
Semaphorin family proteins act on cells to mediate both repulsive and attractive guidance via binding to plexin family receptors, thereby playing fundamental roles in the morphogenesis and homeostasis of various tissues. Although semaphorin-plexin signaling is implicated in various diseases and is thus a target of intensive research, our mechanistic understanding of how semaphorins activate plexins on the cell surface is limited. Here, we describe unique anti-plexin-A1 antibodies that can induce a collapsed morphology in mouse dendritic cells as efficiently as the semaphorin 3A (Sema3A) ligand. Precise epitope analysis indicates that these "semaphorin-mimicking" antibodies dimerize cell-surface plexin-A1 by binding to the N-terminal sema domain of the plexin at sites away from the interface used by the Sema3A ligand. Structural analysis of plexin-A1 fragments using negative stain electron microscopy further revealed that this agonistic capacity is closely linked to the location and orientation of antibody binding. In addition, the full-length plexin-A1 ectodomain exhibited a highly curved "C" shape, reinforcing the very unusual dimeric receptor conformation of this protein at the cell surface when engaged with Sema3A or agonistic antibodies.
Laboratory of Protein Synthesis and Expression, Institute for Protein Research, Osaka University, Suita, Osaka, Japan.
Kei
K
Suzuki
Research Division, Chugai Pharmaceutical Co. Ltd, Gotemba, Shizuoka, Japan.
Hiroyuki
H
Tsunoda
Research Division, Chugai Pharmaceutical Co. Ltd, Gotemba, Shizuoka, Japan.
Ryusuke
R
Omiya
Laboratory of Protein Synthesis and Expression, Institute for Protein Research, Osaka University, Suita, Osaka, Japan.
Kyoko
K
Matoba
Research Division, Chugai Pharmaceutical Co. Ltd, Gotemba, Shizuoka, Japan.
Takeshi
T
Baba
Research Division, Chugai Pharmaceutical Co. Ltd, Gotemba, Shizuoka, Japan.
Sachiyo
S
Suzuki
Research Division, Chugai Pharmaceutical Co. Ltd, Gotemba, Shizuoka, Japan.
Hiroaki
H
Segawa
Department of Respiratory Medicine, Allergy, and Rheumatic Disease, Graduate School of Medicine, Osaka University, Suita, Osaka, Japan.
Atsushi
A
Kumanogoh
Laboratory of Protein Synthesis and Expression, Institute for Protein Research, Osaka University, Suita, Osaka, Japan.
Kenji
K
Iwasaki
Research Division, Chugai Pharmaceutical Co. Ltd, Gotemba, Shizuoka, Japan.
Kunihiro
K
Hattori
Laboratory of Protein Synthesis and Expression, Institute for Protein Research, Osaka University, Suita, Osaka, Japan.
Junichi
J
Takagi
D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry*; D002462:Cell Membrane / Q000378:metabolism; D003713:Dendritic Cells / Q000166:cytology; D018604:Epitope Mapping; D000939:Epitopes; D006801:Humans; D051379:Mice; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000276:immunology*; D000072417:Protein Domains; D055503:Protein Multimerization; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000276:immunology*; D040121:Semaphorin-3A / Q000737:chemistry*; D039961:Semaphorins / Q000737:chemistry*; D015398:Signal Transduction
D000911:Antibodies, Monoclonal; D000939:Epitopes; D009419:Nerve Tissue Proteins; C492116:PLXNA1 protein, human; C492114:Plxna1 protein, mouse; D011956:Receptors, Cell Surface; C488217:Sema3a protein, mouse; D040121:Semaphorin-3A; D039961:Semaphorins