Insulin can induce the expression of a memory-related synaptic protein through facilitating AMPA receptor endocytosis in rat cortical neurons.
Learning and memory depend on long-term synaptic plasticity including long-term potentiation (LTP) and depression (LTD). Activity-regulated cytoskeleton-associated protein (Arc) plays versatile roles in synaptic plasticity mainly through inducing F-actin formation, underlying consolidation of LTP, and promoting AMPA receptor (AMPAR) endocytosis, underlying LTD. Insulin can also induce LTD by facilitating the internalization of AMPARs. In neuroblastoma cells, insulin induced a dramatic increase in Arc mRNA and Arc protein levels, which may underlie the memory-enhancing action of insulin. Thus, a hypothesis was made that, in response to insulin, increased AMPAR endocytosis leads to enhanced Arc expression, and vice versa. Primary cultures of neonatal Sprague-Dawley rat cortical neurons were used. Using Western-blot analysis and immunofluorescent staining, our results reveal that inhibiting AMPAR-mediated responses with AMPAR antagonists significantly enhanced whereas blocking AMPAR endocytosis with various reagents significantly prevented insulin (200 nM, 2 h)-induced Arc expression. Furthermore, via surface biotinylation assay, we demonstrate that acute blockade of new Arc synthesis after insulin stimulation using Arc antisense oligodeoxynucleotide prevented insulin-stimulated AMPAR endocytosis. These findings suggest for the first time that an interaction exists between insulin-stimulated AMPAR endocytosis and insulin-induced Arc expression.
Department of Physiology, School of Medicine, College of Medicine, Kaohsiung Medical University, 100 Shih-Chuan 1st Road, Kaohsiung, 807, Taiwan, tsanju@kmu.edu.tw.
Tsan-Ju
TJ
Chen
Dean-Chuan
DC
Wang
Hui-Shan
HS
Hung
Hsuan-Fang
HF
Ho
D000818:Animals; D002478:Cells, Cultured; D002966:Clathrin / Q000378:metabolism; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D004705:Endocytosis / Q000187:drug effects*; D005786:Gene Expression Regulation / Q000187:drug effects*; D007328:Insulin / Q000494:pharmacology*; D017774:Long-Term Potentiation / Q000187:drug effects; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009473:Neuronal Plasticity / Q000187:drug effects; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D020319:Oligodeoxyribonucleotides, Antisense / Q000494:pharmacology; D011810:Quinoxalines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018091:Receptors, AMPA / Q000037:antagonists & inhibitors / Q000378:metabolism*; D019061:src-Family Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
D002966:Clathrin; D003598:Cytoskeletal Proteins; D007328:Insulin; D009419:Nerve Tissue Proteins; D020319:Oligodeoxyribonucleotides, Antisense; D011810:Quinoxalines; D018091:Receptors, AMPA; C092069:activity regulated cytoskeletal-associated protein; C062865:2,3-dioxo-6-nitro-7-sulfamoylbenzo(f)quinoxaline; D019061:src-Family Kinases; C104722:glutamate receptor ionotropic, AMPA 2