title: Liprin-alpha has LAR-independent functions in R7 photoreceptor axon targeting.
abstract: In the Drosophila visual system, the color-sensing photoreceptors R7 and R8 project their axons to two distinct layers in the medulla. Loss of the receptor tyrosine phosphatase LAR from R7 photoreceptors causes their axons to terminate prematurely in the R8 layer. Here we identify a null mutation in the Liprin-alpha gene based on a similar R7 projection defect. Liprin-alpha physically interacts with the inactive D2 phosphatase domain of LAR, and this domain is also essential for R7 targeting. However, another LAR-dependent function, egg elongation, requires neither Liprin-alpha nor the LAR D2 domain. Although human and Caenorhabditis elegans Liprin-alpha proteins have been reported to control the localization of LAR, we find that LAR localizes to focal adhesions in Drosophila S2R+ cells and to photoreceptor growth cones in vivo independently of Liprin-alpha. In addition, Liprin-alpha overexpression or loss of function can affect R7 targeting in the complete absence of LAR. We conclude that Liprin-alpha does not simply act by regulating LAR localization but also has LAR-independent functions.
authors.affiliation: Skirball Institute for Biomolecular Medicine, Department of Cell Biology, New York University School of Medicine, New York, NY 10016, USA.
authors.forename: Kerstin
authors.initials: K
authors.lastname: Hofmeyer
authors.forename: Corinne
authors.initials: C
authors.lastname: Maurel-Zaffran
authors.forename: Helen
authors.initials: H
authors.lastname: Sink
authors.forename: Jessica E
authors.initials: JE
authors.lastname: Treisman
mesh_terms: D000818:Animals; D001369:Axons / Q000378:metabolism / Q000648:ultrastructure; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000033:anatomy & histology / Q000196:embryology; D005260:Female; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D009024:Morphogenesis; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D017956:Photoreceptor Cells, Invertebrate / Q000166:cytology / Q000196:embryology; D017027:Protein Tyrosine Phosphatases / Q000235:genetics / Q000378:metabolism*; D054623:Receptor-Like Protein Tyrosine Phosphatases, Class 2; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism*; D012160:Retina / Q000166:cytology / Q000196:embryology / Q000378:metabolism; D019076:Transgenes
chemical_list: D029721:Drosophila Proteins; D047908:Intracellular Signaling Peptides and Proteins; C490600:Liprin-alpha protein, Drosophila; D009419:Nerve Tissue Proteins; D010750:Phosphoproteins; D011956:Receptors, Cell Surface; C516772:PTPRF protein, human; D017027:Protein Tyrosine Phosphatases; D054623:Receptor-Like Protein Tyrosine Phosphatases, Class 2