title: Glutamate-induced internalization of Ca(v)1.3 L-type Ca(2+) channels protects retinal neurons against excitotoxicity.
abstract: Glutamate-induced rise in the intracellular Ca(2+) level is thought to be a major cause of excitotoxic cell death, but the mechanisms that control the Ca(2+) overload are poorly understood. Using immunocytochemistry, electrophysiology and Ca(2+) imaging, we show that activation of ionotropic glutamate receptors induces a selective internalization of Ca(v)1.3 L-type Ca(2+) channels in salamander retinal neurons. The effect of glutamate on Ca(v)1.3 internalization was blocked in Ca(2+)-free external solution, or by strong buffering of internal Ca(2+) with BAPTA. Downregulation of L-type Ca(2+) channel activity in retinal ganglion cells by glutamate was suppressed by inhibitors of dynamin-dependent endocytosis. Stabilization of F-actin by jasplakinolide significantly reduced the ability of glutamate to induce internalization suggesting it is mediated by Ca(2+)-dependent reorganization of actin cytoskeleton. We showed that the Ca(v)1.3 is the primary L-type Ca(2+) channel contributing to kainate-induced excitotoxic death of amacrine and ganglion cells. Block of Ca(v)1.3 internalization by either dynamin inhibition or F-actin stabilization increased vulnerability of retinal amacrine and ganglion cells to kainate-induced excitotoxicity. Our data show for the first time that Ca(v)1.3 L-type Ca(2+) channels are subject to rapid glutamate-induced internalization, which may serve as a negative feedback mechanism protecting retinal neurons against glutamate-induced excitotoxicity.
authors.affiliation: Department of Ophthalmology, NYU Medical Center, New York, NY 10016, USA.
authors.forename: Fengxia
authors.initials: F
authors.lastname: Mizuno
authors.forename: Peter
authors.initials: P
authors.lastname: Barabas
authors.forename: David
authors.initials: D
authors.lastname: Krizaj
authors.forename: Abram
authors.initials: A
authors.lastname: Akopian
mesh_terms: D000818:Animals; D020746:Calcium Channels, L-Type / Q000378:metabolism*; D003599:Cytoskeleton / Q000502:physiology; D034281:Dynamins / Q000378:metabolism; D055724:Electrophysiological Phenomena / Q000502:physiology; D025461:Feedback, Physiological / Q000502:physiology*; D018698:Glutamic Acid / Q000009:adverse effects / Q000494:pharmacology*; D018408:Patch-Clamp Techniques; D017470:Receptors, Glutamate / Q000187:drug effects / Q000378:metabolism; D055351:Retinal Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D014562:Caudata
chemical_list: D020746:Calcium Channels, L-Type; D017470:Receptors, Glutamate; D018698:Glutamic Acid; D034281:Dynamins