The C. elegans L1CAM homologue LAD-2 functions as a coreceptor in MAB-20/Sema2 mediated axon guidance.
The L1 cell adhesion molecule (L1CAM) participates in neuronal development. Mutations in the human L1 gene can cause the neurological disorder CRASH (corpus callosum hypoplasia, retardation, adducted thumbs, spastic paraplegia, and hydrocephalus). This study presents genetic data that shows that L1-like adhesion gene 2 (LAD-2), a Caenorhabditis elegans L1CAM, functions in axon pathfinding. In the SDQL neuron, LAD-2 mediates dorsal axon guidance via the secreted MAB-20/Sema2 and PLX-2 plexin receptor, the functions of which have largely been characterized in epidermal morphogenesis. We use targeted misexpression experiments to provide in vivo evidence that MAB-20/Sema2 acts as a repellent to SDQL. Coimmunoprecipitation assays reveal that MAB-20 weakly interacts with PLX-2; this interaction is increased in the presence of LAD-2, which can interact independently with MAB-20 and PLX-2. These results suggest that LAD-2 functions as a MAB-20 coreceptor to secure MAB-20 coupling to PLX-2. In vertebrates, L1 binds neuropilin1, the obligate receptor to the secreted Sema3A. However, invertebrates lack neuropilins. LAD-2 may thus function in the semaphorin complex by combining the roles of neuropilins and L1CAMs.
Wang
Xuelin
X
Department of Genetics, Cell Biology, and Development, Developmental Biology Center, University of Minnesota, Minneapolis, MN 55455, USA.
Zhang
Wei
W
Cheever
Thomas
T
Schwarz
Valentin
V
Opperman
Karla
K
Hutter
Harald
H
Koepp
Deanna
D
Chen
Lihsia
L
D000595:Amino Acid Sequence; D000818:Animals; D001369:Axons / Q000378:metabolism*; D017173:Caenorhabditis elegans / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D008565:Membrane Proteins / Q000378:metabolism* / Q000502:physiology; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000378:metabolism* / Q000502:physiology; D039842:Neural Cell Adhesion Molecule L1 / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D019006:Neural Cell Adhesion Molecules / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism; D016415:Sequence Alignment; D015398:Signal Transduction
D029742:Caenorhabditis elegans Proteins; C526374:LAD-2 protein, C elegans; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D039842:Neural Cell Adhesion Molecule L1; D019006:Neural Cell Adhesion Molecules; C526375:Plx-2 protein, C elegans; D011956:Receptors, Cell Surface; C501528:SAX-7 protein, C elegans; C405025:mab-20 protein, C elegans