title: The receptor phosphatase HmLAR2 collaborates with focal adhesion proteins in filopodial tips to control growth cone morphology.
abstract: Receptor protein tyrosine phosphatases (RPTPs) have been shown to play key roles in regulating axon guidance and synaptogenesis. HmLAR2, one of two closely related LAR-like RPTPs in the embryonic leech, is expressed in a few central neurons and in a unique segmentally-iterated peripheral cell, the comb cell (CC). Here we show that tagged HmLAR2-EGFP has a punctate pattern of expression in the growth cones of the CC, particularly at the tips of extending filopodia. Moreover, although expression of the wild-type EGFP-tagged receptor does not affect CC growth cone morphology, expression of a putative dominant-negative mutant of the receptor, CS-HmLAR2, leads to the enlargement of the growth cones, a shortening of filopodia, and errors in cellular tiling. RNAi of several candidate substrate signaling proteins, Lena (leech Ena/Vasp), beta-integrin and paxillin, but not beta-catenin, phenocopies particular aspects of the effects of HmLAR2 RNAi. For paxillin, which co-localizes with HmLAR2 at growth cone puncta, knock-down led to a reduction in the number of such puncta. Together, our data suggests that HmLAR2 regulates the morphology of the growth cone by controlling F-actin polymerization and focal adhesion complexes.
authors.affiliation: Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, CA 92093, USA. mwbaker@ucsd.edu
authors.forename: Michael W
authors.initials: MW
authors.lastname: Baker
authors.forename: Sandra M
authors.initials: SM
authors.lastname: Peterson
authors.forename: Eduardo R
authors.initials: ER
authors.lastname: Macagno
mesh_terms: D000818:Animals; D016466:CHO Cells; D002384:Catalysis; D006224:Cricetinae; D003412:Cricetulus; D022001:Focal Adhesions / Q000201:enzymology*; D018507:Gene Expression Regulation, Developmental; D049452:Green Fluorescent Proteins / Q000378:metabolism; D020439:Growth Cones / Q000201:enzymology*; D007865:Leeches / Q000166:cytology / Q000196:embryology / Q000201:enzymology* / Q000235:genetics; D009154:Mutation / Q000235:genetics; D051419:Paxillin / Q000378:metabolism; D010641:Phenotype; D019000:Phosphotyrosine / Q000378:metabolism; D011485:Protein Binding; D021381:Protein Transport; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism*; D011554:Pseudopodia / Q000201:enzymology*; D034622:RNA Interference; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015398:Signal Transduction; D019076:Transgenes
chemical_list: D051419:Paxillin; D011993:Recombinant Fusion Proteins; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D019000:Phosphotyrosine; C111444:HmLAR2 protein, Hirudo medicinalis; D017027:Protein Tyrosine Phosphatases