Identification of domains of netrin UNC-6 that mediate attractive and repulsive guidance and responses from cells and growth cones.
Netrin UNC-6 is a protein secreted from ventral cells that guides cell and growth cone migrations in Caenorhabditis elegans. Previously it was shown that UNC-6 domain V-2 regulates dorsal guidance activity and domain C regulates an activity that prevents the branching of axons when they respond to the N-terminal domains. Because these results indicate that the biological activities of UNC-6 are mediated through specific domains, we systematically examined each UNC-6 domain for guidance activities. Transgenic animals expressing UNC-6 derivatives with domain deletions and mutants with selective unc-6 loss-of-function mutations were analyzed. The results indicate that the VI, V-2, and V-3 domains are primarily required for dorsal migrations and the VI and V-3 domains are required for ventral migrations. These domains are likely important for responses mediated by the UNC-5 and UNC-40 receptors, respectively. Deletion of V-3 and a V-3 point mutation selectively affect either cell or growth cone migrations, indicating that each migration requires unique interactions with UNC-6. Deletion of domain VI or of a conserved eight amino acid motif within VI causes loss of all UNC-6 guidance activities, and mutations within domain VI selectively affect different guidance activities, suggesting that domain VI regulates each response to UNC-6. We propose that individual UNC-6 domains mediate different signals, which act in parallel to regulate the morphological changes necessary for guidance.
Lim
Yoo-shick
YS
Department of Pathology, Robert Wood Johnson Medical School, Piscataway, New Jersey 08854-5635, USA.
Wadsworth
William G
WG
D000483:Alleles; D020816:Amino Acid Motifs / Q000502:physiology; D000818:Animals; D030801:Animals, Genetically Modified; D001369:Axons / Q000502:physiology; D017173:Caenorhabditis elegans; D029742:Caenorhabditis elegans Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D002465:Cell Movement / Q000502:physiology; D020439:Growth Cones / Q000502:physiology* / Q000648:ultrastructure; D015801:Helminth Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D016297:Mutagenesis, Site-Directed; D009414:Nerve Growth Factors / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D009419:Nerve Tissue Proteins; D000075385:Netrins; D010641:Phenotype; D017434:Protein Structure, Tertiary / Q000502:physiology; D017384:Sequence Deletion; D013329:Structure-Activity Relationship; D019076:Transgenes
D029742:Caenorhabditis elegans Proteins; D015801:Helminth Proteins; D009414:Nerve Growth Factors; D009419:Nerve Tissue Proteins; D000075385:Netrins; C078146:UNC-6 protein, C elegans