title: Prenatal cocaine exposure increases synaptic localization of a neuronal RasGEF, GRASP-1 via hyperphosphorylation of AMPAR anchoring protein, GRIP.
abstract: Prenatal cocaine exposure causes sustained phosphorylation of the synaptic anchoring protein, glutamate receptor interacting protein (GRIP1/2), preventing synaptic targeting of the GluR2/3-containing alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-type glutamate receptors (AMPARs; J. Neurosci. 29: 6308-6319, 2009). Because overexpression of GRIP-associated neuronal rasGEF protein (GRASP-1) specifically reduces the synaptic targeting of AMPARs, we hypothesized that prenatal cocaine exposure enhances GRASP-1 synaptic membrane localization leading to hyper-activation of ras family proteins and heightened actin polymerization. Our results show a markedly increased GRIP1-associated GRASP-1 content with approximately 40% reduction in its rasGEF activity in frontal cortices (FCX) of 21-day-old (P21) prenatal cocaine-exposed rats. This cocaine effect is the result of a persistent protein kinase C (PKC)- and downstream Src tyrosine kinase-mediated GRIP phosphorylation. The hyperactivated PKC also increased membrane-associated GRASP-1 and activated small G-proteins RhoA, cdc42/Rac1 and Rap1 as well as filamentous actin (F-actin) levels without an effect on the phosphorylation state of actin. Since increased F-actin facilitates protein transport, our results suggest that increased GRASP-1 synaptic localization in prenatal cocaine-exposed brains is an adaptive response to restoring the synaptic expression of AMPA-GluR2/3. Our earlier data demonstrated that persistent PKC-mediated GRIP phosphorylation reduces GluR2/3 synaptic targeting in prenatal cocaine-exposed brains, we now show that the increased GRIP-associated GRASP-1 may contribute to the reduction in GluR2/3 synaptic expression and AMPAR signaling defects.
authors: Department of Physiology, Pharmacology and Neuroscience, Sophie Davis School of Biomedical Education, The City University of New York Medical School, New York, New York, United States of America.
authors: Kalindi
authors: K
authors: Bakshi
authors: Mary
authors: M
authors: Kosciuk
authors: Robert G
authors: RG
authors: Nagele
authors: Eitan
authors: E
authors: Friedman
authors: Hoau-Yan
authors: HY
authors: Wang
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D001921:Brain / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism*; D003042:Cocaine / Q000633:toxicity*; D005260:Female; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D036341:Intercellular Signaling Peptides and Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D018811:Maternal Exposure / Q000009:adverse effects*; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism*; D009924:Organ Culture Techniques; D010766:Phosphorylation; D011247:Pregnancy; D011485:Protein Binding; D051381:Rats; D017207:Rats, Sprague-Dawley; D018091:Receptors, AMPA; D013574:Synaptosomes / Q000378:metabolism; D020744:rac GTP-Binding Proteins; D020663:ras Guanine Nucleotide Exchange Factors / Q000378:metabolism*
chemical_list: D000199:Actins; D002352:Carrier Proteins; C491308:Grip1 protein, rat; C118486:Grip2 protein, rat; D036341:Intercellular Signaling Peptides and Proteins; D047908:Intracellular Signaling Peptides and Proteins; D009419:Nerve Tissue Proteins; D018091:Receptors, AMPA; D020663:ras Guanine Nucleotide Exchange Factors; D020744:rac GTP-Binding Proteins; D003042:Cocaine; C104722:glutamate receptor ionotropic, AMPA 2