title: Plexin-B1/RhoGEF-mediated RhoA activation involves the receptor tyrosine kinase ErbB-2.
abstract: Plexins are widely expressed transmembrane proteins that mediate the effects of semaphorins. The molecular mechanisms of plexin-mediated signal transduction are still rather unclear. Plexin-B1 has recently been shown to mediate activation of RhoA through a stable interaction with the Rho guanine nucleotide exchange factors PDZ-RhoGEF and LARG. However, it is unclear how the activity of plexin-B1 and its downstream effectors is regulated by its ligand Sema4D. Here, we show that plexin-B family members stably associate with the receptor tyrosine kinase ErbB-2. Binding of Sema4D to plexin-B1 stimulates the intrinsic tyrosine kinase activity of ErbB-2, resulting in the phosphorylation of both plexin-B1 and ErbB-2. A dominant-negative form of ErbB-2 blocks Sema4D-induced RhoA activation as well as axonal growth cone collapse in primary hippocampal neurons. Our data indicate that ErbB-2 is an important component of the plexin-B receptor system and that ErbB-2-mediated phosphorylation of plexin-B1 is critically involved in Sema4D-induced RhoA activation, which underlies cellular phenomena downstream of plexin-B1, including axonal growth cone collapse.
authors.affiliation: Institute of Pharmacology, University of Heidelberg, Im Neuenheimer Feld 366, 69120 Heidelberg, Germany.
authors.forename: Jakub M
authors.initials: JM
authors.lastname: Swiercz
authors.forename: Rohini
authors.initials: R
authors.lastname: Kuner
authors.forename: Stefan
authors.initials: S
authors.lastname: Offermanns
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D019556:COS Cells; D002455:Cell Division; D002522:Chlorocebus aethiops; D002846:Chromatography, Affinity; D004789:Enzyme Activation; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D010766:Phosphorylation; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism*; D064067:Rho Guanine Nucleotide Exchange Factors; D020742:rhoA GTP-Binding Protein / Q000378:metabolism*
chemical_list: D000469:Alkaline Phosphatase; D020662:Guanine Nucleotide Exchange Factors; D009419:Nerve Tissue Proteins; D018719:Erb-b2 Receptor Tyrosine Kinases; D011956:Receptors, Cell Surface; D064067:Rho Guanine Nucleotide Exchange Factors; D020742:rhoA GTP-Binding Protein; C492119:PLXNB1 protein, human