Mutant SOD1 forms ion channel: Implications for ALS pathophysiology

作者：Allen Michael J; Lacroix Jerome J; Ramachandran Srinivasan; Capone Ricardo; Whitlock Jenny L; Ghadge Ghanashyam D; Arnsdorf Morton F; Roos Raymond P^*; Lal Ratnesh

来源：Neurobiology of Disease, 2012, 45(3): 831-838.

DOI：10.1016/j.nbd.2011.08.031

• Amyotrophic lateral sclerosis
• Superoxide dismutase
• A4V
• Protein misfolding
• Atomic force microscopy
• Fluo-4 calcium assay
• DiBAC(4)(3) membrane potential measurement

Point mutations in the gene encoding copper-zinc superoxide dismutase (SOD1) impart a gain-of-function to this protein that underlies 20-25% of all familial amyotrophic lateral sclerosis (FALS) cases. However, the specific mechanism of mutant SOD1 toxicity has remained elusive. Using the complementary techniques of atomic force microscopy (AFM), electrophysiology, and cell and molecular biology, here we examine the structure and activity of A4VSOD1, a mutant SOD1. AFM of A4VSOD1 reconstituted in lipid membrane shows discrete tetrameric pore-like structure with outer and inner diameters 12.2 and 3.0 nm respectively. Electrophysiological recordings show distinct ionic conductances across bilayer for A4VSOD1 and none for wildtype SOD1. Mouse neuroblastoma cells exposed to A4VSOD1 undergo membrane depolarization and increases in intracellular calcium. These results provide compelling new evidence that a mutant SOD1 is capable of disrupting cellular homeostasis via an unregulated ion channel mechanism. Such a "toxic channel" mechanism presents a new therapeutic direction for ALS research.

• 出版日期2012-3