ApoSOD1 lacking dismutase activity neuroprotects motor neurons exposed to beta-methylamino-L-alanine through the Ca2+/Akt/ERK1/2 prosurvival pathway

Cell Death Differ. 2017 Mar;24(3):511-522. doi: 10.1038/cdd.2016.154. Epub 2017 Jan 13.

Abstract

Amyotrophic lateral sclerosis (ALS) is a severe human adult-onset neurodegenerative disease affecting lower and upper motor neurons. In >20% of cases, the familial form of ALS is caused by mutations in the gene encoding Cu,Zn-superoxide dismutase (SOD1). Interestingly, administration of wild-type SOD1 to SOD1G93A transgenic rats ameliorates motor symptoms through an unknown mechanism. Here we investigated whether the neuroprotective effects of SOD1 are due to the Ca2+-dependent activation of such prosurvival signaling pathway and not to its catalytic activity. To this aim, we also examined the mechanism of neuroprotective action of ApoSOD1, the metal-depleted state of SOD1 that lacks dismutase activity, in differentiated motor neuron-like NSC-34 cells and in primary motor neurons exposed to the cycad neurotoxin beta-methylamino-L-alanine (L-BMAA). Preincubation of ApoSOD1 and SOD1, but not of human recombinant SOD1G93A, prevented cell death in motor neurons exposed to L-BMAA. Moreover, ApoSOD1 elicited ERK1/2 and Akt phosphorylation in motor neurons through an early increase of intracellular Ca2+ concentration ([Ca2+]i). Accordingly, inhibition of ERK1/2 by siMEK1 and PD98059 counteracted ApoSOD1- and SOD1-induced neuroprotection. Similarly, transfection of the dominant-negative form of Akt in NSC-34 motor neurons and treatment with the selective PI3K inhibitor LY294002 prevented ApoSOD1- and SOD1-mediated neuroprotective effects in L-BMAA-treated motor neurons. Furthermore, ApoSOD1 and SOD1 prevented the expression of the two markers of L-BMAA-induced ER stress GRP78 and caspase-12. Collectively, our data indicate that ApoSOD1, which is devoid of any catalytic dismutase activity, exerts a neuroprotective effect through an early activation of Ca2+/Akt/ERK1/2 pro-survival pathway that, in turn, prevents ER stress in a neurotoxic model of ALS.

MeSH terms

  • Amino Acids, Diamino / toxicity*
  • Animals
  • Apoproteins / chemistry
  • Apoproteins / genetics
  • Apoproteins / metabolism
  • Calcium / metabolism
  • Cell Survival / drug effects
  • Cells, Cultured
  • Cyanobacteria Toxins
  • Endoplasmic Reticulum Chaperone BiP
  • Flavonoids / pharmacology
  • Heat-Shock Proteins / metabolism
  • Humans
  • MAP Kinase Kinase 1 / antagonists & inhibitors
  • MAP Kinase Kinase 1 / genetics
  • MAP Kinase Kinase 1 / metabolism
  • Mice
  • Mice, Inbred C57BL
  • Mitogen-Activated Protein Kinase 1 / metabolism*
  • Mitogen-Activated Protein Kinase 3 / metabolism*
  • Motor Neurons / cytology
  • Motor Neurons / metabolism
  • Neuroprotective Agents / metabolism
  • Phosphatidylinositol 3-Kinases / metabolism
  • Phosphoinositide-3 Kinase Inhibitors
  • Proto-Oncogene Proteins c-akt / metabolism*
  • Rats
  • Recombinant Proteins / biosynthesis
  • Recombinant Proteins / isolation & purification
  • Recombinant Proteins / pharmacology
  • Superoxide Dismutase-1 / chemistry
  • Superoxide Dismutase-1 / genetics
  • Superoxide Dismutase-1 / metabolism*
  • Tretinoin / pharmacology

Substances

  • Amino Acids, Diamino
  • Apoproteins
  • Cyanobacteria Toxins
  • Endoplasmic Reticulum Chaperone BiP
  • Flavonoids
  • HSPA5 protein, human
  • Heat-Shock Proteins
  • Hspa5 protein, mouse
  • Neuroprotective Agents
  • Phosphoinositide-3 Kinase Inhibitors
  • Recombinant Proteins
  • beta-N-methylamino-L-alanine
  • Tretinoin
  • Superoxide Dismutase-1
  • Proto-Oncogene Proteins c-akt
  • Mitogen-Activated Protein Kinase 1
  • Mitogen-Activated Protein Kinase 3
  • MAP Kinase Kinase 1
  • 2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one
  • Calcium