Activity-dependent regulation of mitochondrial motility by calcium and Na/K-ATPase at nodes of Ranvier of myelinated nerves.
The node of Ranvier is a tiny segment of a myelinated fiber with various types of specializations adapted for generation of high-speed nerve impulses. It is ionically specialized with respect to ion channel segregation and ionic fluxes, and metabolically specialized in ionic pump expression and mitochondrial density augmentation. This report examines the interplay of three important parameters (calcium fluxes, Na pumps, mitochondrial motility) at nodes of Ranvier in frog during normal nerve activity. First, we used calcium dyes to resolve a highly localized elevation in axonal calcium at a node of Ranvier during action potentials, and showed that this calcium elevation retards mitochondrial motility during nerve impulses. Second, we found, surprisingly, that physiologic activation of the Na pumps retards mitochondrial motility. Blocking Na pumps alone greatly prevents action potentials from retarding mitochondrial motility, which reveals that mitochondrial motility is coupled to Na/K-ATPase. In conclusion, we suggest that during normal nerve activity, Ca elevation and activation of Na/K-ATPase act, possibly in a synergistic manner, to recruit mitochondria to a node of Ranvier to match metabolic needs.
Zhang
Chuan Li
CL
Department of Physiology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53706, USA.
Ho
Po Lai
PL
Kintner
Douglas B
DB
Sun
Dandan
D
Chiu
Shing Yan
SY
D000200:Action Potentials / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D002118:Calcium / Q000502:physiology*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D008297:Male; D008928:Mitochondria / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D009413:Nerve Fibers, Myelinated / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D011901:Ranvier's Nodes / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000502:physiology*; D014982:Xenopus laevis
D002121:Calcium Channel Blockers; D000254:Sodium-Potassium-Exchanging ATPase; D002118:Calcium