title: Antibody/receptor protein immunocomplex in human and mouse cortical nerve endings amplifies complement-induced glutamate release.
abstract: Previous studies have demonstrated that complement alone releases glutamate from human and mouse cortical terminals in an antibody-independent manner. In order to expand our knowledge on complement-mediated effects, we investigated whether the presence of an antigen-antibody complex in synaptosomal plasmamembranes could also trigger complement-induced functional responses that might affect neurotransmitter release. To this aim, we focused on the chemokine 5 receptor (CCR5) expressed in human and mouse cortical glutamate terminals, whose activation by CCL5 elicits [(3)H]D-aspartate ([(3)H]D-ASP) release. Preincubating synaptosomes with an antibody recognizing the NH2 terminus of the CCR5 protein (anti-NH2-CCR5 antibody) abolished the CCL5-induced [(3)H]D-ASP release. Similarly, enriching synaptosomes with an antibody recognizing the COOH terminus of CCR5 (anti-COOH-CCR5 antibody) prevented the CCL5-induced [(3)H]D-ASP release. The antagonist-like activity of the anti-NH2-CCR5 antibody turned to facilitation when anti-NH2-CCR5-treated synaptosomes were exposed to complement. In these terminals, the releasing effect was significantly higher than that elicited by complement in untreated synaptosomes. On the contrary, the complement-induced [(3)H]D-ASP release from anti-COOH-CCR5 antibody-entrapped synaptosomes did not differ from that from untreated synaptosomes. Preincubating synaptosomes with anti-beta tubulin III antibody, used as negative control, neither prevented the CCL5-induced releasing effect nor it amplified the complement-induced [(3)H]D-ASP release. Finally, serum lacking the C1q protein, i.e. the protein essential to promote the antibody-mediated activation of complement, elicited a comparable [(3)H]D-ASP release from both untreated and anti-NH2-CCR5 antibody-treated synaptosomes. Thus, we propose that antibodies raised against the outer sequence of a receptor protein can trigger the activation of the complement through the classic, C1q-mediated antibody-dependent pathway, which results in an abnormal release of glutamate that could be deleterious to central nervous system.
authors.affiliation: Department of Pharmacy, Pharmacology and Toxicology Section, University of Genoa, Genoa, Italy.
authors.forename: Elisa
authors.initials: E
authors.lastname: Merega
authors.affiliation: Department of Pharmacy, Pharmacology and Toxicology Section, University of Genoa, Genoa, Italy.
authors.forename: Silvia Di
authors.initials: SD
authors.lastname: Prisco
authors.affiliation: Division of Neurosurgery, Galliera Hospital, Genoa, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Severi
authors.affiliation: Division of Neurosurgery, Galliera Hospital, Genoa, Italy.
authors.forename: Fotios
authors.initials: F
authors.lastname: Kalfas
authors.affiliation: Department of Pharmacy, Pharmacology and Toxicology Section, University of Genoa, Genoa, Italy; Center of Excellence for Biomedical Research, University of Genoa, Genoa, Italy. Electronic address: pittalug@pharmatox.unige.it.
authors.forename: Anna
authors.initials: A
authors.lastname: Pittaluga
mesh_terms: D000328:Adult; D000368:Aged; D000818:Animals; D000906:Antibodies / Q000494:pharmacology*; D001224:Aspartic Acid / Q000378:metabolism; D002540:Cerebral Cortex / Q000187:drug effects* / Q000378:metabolism; D018946:Chemokine CCL5 / Q000378:metabolism / Q000494:pharmacology; D015922:Complement C1q / Q000378:metabolism*; D003171:Complement Pathway, Classical; D005260:Female; D018698:Glutamic Acid / Q000378:metabolism*; D006801:Humans; D008297:Male; D008810:Mice, Inbred C57BL; D008875:Middle Aged; D009411:Nerve Endings / Q000187:drug effects* / Q000378:metabolism; D019713:Receptors, CCR5 / Q000276:immunology*; D013045:Species Specificity; D013574:Synaptosomes / Q000378:metabolism
chemical_list: D000906:Antibodies; D018946:Chemokine CCL5; D019713:Receptors, CCR5; D001224:Aspartic Acid; D018698:Glutamic Acid; D015922:Complement C1q
keywords: Anti-ccr5 antibody; BBB; CCR5; CCRs; Complement; C–C chemokine receptors; Glutamate; Human cortex; Mouse cortex; RANTES; blood-brain barrier; expressed and secreted; regulated upon activation normal T cells