title: Depalmitoylation preferentially downregulates AMPA induced Ca2+ signaling and neurotoxicity in motor neurons.
abstract: Excessive activation of AMPA receptor has been implicated in motor neuron degeneration in amyotrophic lateral sclerosis (ALS). However, it is not clear why motor neurons are preferentially sensitive to AMPA receptor mediated excessive [Ca(2+)]i rise and excitotoxicity. In the present study we examined whether palmitoylation regulates Ca(2+) permeability of AMPA receptor and excitotoxicity in cultured spinal cord neurons. We adapted chronic 2-bromopalmitate (2-BrP) treatment to achieve depalmitoylation and examined its effect on the cytotoxicity in spinal cord neurons exposed to AMPA. The change in AMPA induced signaling and cytotoxicity in motor neurons and other spinal neurons under identical conditions of exposure to AMPA was studied. 2-BrP treatment inhibited AMPA induced rise in [Ca(2+)]i and cytotoxicity in both types of neurons but the degree of inhibition was significantly higher in motor neurons as compared to other spinal neurons. The AMPA induced [Na(+)]i rise was moderately affected in both type of neurons on depalmitoylation. Depalmitoylation reduced the expression levels of AMPA receptor subunits (GluR1 and GluR2) and also PSD-95 but stargazin levels remained unaffected. Our results demonstrate that 2-BrP attenuates AMPA receptor activated Ca(2+) signaling and cytotoxicity preferentially in motor neurons and suggest that AMPA receptor modulation by depalmitoylation could play a significant role in preventing motor neuron degeneration.
authors.affiliation: Department of Biophysics, National Institute of Mental Health and Neuro Sciences, Bangalore 560029, India.
authors.forename: Karthik
authors.initials: K
authors.lastname: Krishnamurthy
authors.forename: Bhupesh
authors.initials: B
authors.lastname: Mehta
authors.forename: Mahendra
authors.initials: M
authors.lastname: Singh
authors.forename: Bhanu P
authors.initials: BP
authors.lastname: Tewari
authors.forename: Preeti G
authors.initials: PG
authors.lastname: Joshi
authors.forename: Nanda B
authors.initials: NB
authors.lastname: Joshi
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects* / Q000502:physiology; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D000076122:Disks Large Homolog 4 Protein; D004622:Embryo, Mammalian; D007004:Hypoglycemic Agents / Q000633:toxicity; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D054878:Lipoylation / Q000187:drug effects / Q000502:physiology*; D008565:Membrane Proteins / Q000378:metabolism; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D009046:Motor Neurons / Q000187:drug effects* / Q000378:metabolism*; D010168:Palmitates / Q000633:toxicity; D051381:Rats; D017207:Rats, Sprague-Dawley; D018091:Receptors, AMPA / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism; D013116:Spinal Cord / Q000166:cytology; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000494:pharmacology*
chemical_list: D000076122:Disks Large Homolog 4 Protein; C501449:Dlg4 protein, rat; D007004:Hypoglycemic Agents; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D008869:Microtubule-Associated Proteins; D010168:Palmitates; D018091:Receptors, AMPA; C022776:2-bromopalmitate; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; D012964:Sodium; D002118:Calcium
keywords: 2-BrP; 2-Bromopalmitate; AMPA; AMPA receptor; Amyotrophic lateral sclerosis; Calcium signaling; Depalmitoylation; EMEM; Eagle′s minimal essential medium; Excitotoxicity; HBSS; HEPES; Hanks buffered salt saline; Motor neuron; N-2-hydroxyethyl piperazine-n-2-ethanesulphonic acid; TARPs; Transmembrane AMPA receptor regulatory protein; Transmembrane AMPA receptor regulatory proteins; α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid