title: Regulation of ErbB-4 endocytosis by neuregulin in GABAergic hippocampal interneurons.
abstract: Neuregulin (NRG)/ErbB receptor signaling pathways have recently been implicated in the reversal of long-term potentiation at hippocampal glutamatergic synapses. Moreover, polymorphisms in NRG-1 and ErbB-4 genes have been linked to an increased risk for developing schizophrenia. ErbB-4 is highly expressed at glutamatergic synapses where it binds to PSD-95 via its carboxyl terminal T-V-V sequence. Here we investigated the expression, localization and trafficking of ErbB-4 in cultured hippocampal neurons by immunocytochemistry, surface protein biotinylation, and live labeling of native receptors. We show that neuronal ErbB-4 is detected at its highest levels in GABAergic interneurons, as observed in vivo. ErbB-4 immunoreactivity precedes PSD-95 expression, with ErbB-4 cluster initially forming in the absence of, but later associating with, PSD-95-positive puncta. By surface protein biotinylation, the fraction of ErbB-4 receptors on the plasma membrane increases from 30% to 65% between 6 and 16 days in vitro (DIV). Interestingly, 30 min of NRG stimulation triggers measurable ErbB-4 receptor internalization at DIV 16, despite increased colocalization with PSD-95. We also investigated the role of TNFalpha-converting enzyme (TACE)-mediated receptor processing in regulating ErbB-4 surface expression. We found that the cleavage-resistant JM-b isoform accounts for 80% of all ErbB-4 transcripts in cultured hippocampal neurons. Receptor stimulation or treatment with phorbol esters does not induce detectable ErbB-4 processing, indicating that neurons mostly rely on endocytosis of the intact receptor to regulate ErbB-4 surface expression. These results enhance our understanding of the regulation of ErbB-4--mediated signaling at glutamatergic synapses.
authors.affiliation: Section on Molecular Neurobiology, NICHD, Bethesda, MD 20892, USA. mlongart@idea.gob.ve
authors.forename: M
authors.initials: M
authors.lastname: Longart
authors.forename: M
authors.initials: M
authors.lastname: Chatani-Hinze
authors.forename: C M
authors.initials: CM
authors.lastname: Gonzalez
authors.forename: D
authors.initials: D
authors.lastname: Vullhorst
authors.forename: A
authors.initials: A
authors.lastname: Buonanno
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D000076122:Disks Large Homolog 4 Protein; D004705:Endocytosis / Q000502:physiology*; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism*; D051528:Guanylate Kinases; D006624:Hippocampus / Q000166:cytology*; D006801:Humans; D007395:Interneurons / Q000166:cytology / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D020890:Neuregulin-1; D009474:Neurons / Q000737:chemistry / Q000166:cytology / Q000378:metabolism*; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D066247:Receptor, ErbB-4; D015398:Signal Transduction / Q000502:physiology; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
chemical_list: D000076122:Disks Large Homolog 4 Protein; C501447:Dlg4 protein, mouse; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; C094131:NRG1 protein, human; D009419:Nerve Tissue Proteins; D020890:Neuregulin-1; D020033:Protein Isoforms; D005680:gamma-Aminobutyric Acid; C587689:ERBB4 protein, human; D066246:ErbB Receptors; C587690:Erbb4 protein, mouse; C587691:Erbb4 protein, rat; D066247:Receptor, ErbB-4; D051528:Guanylate Kinases