Characteristics of intermittent mitochondrial transport in guinea pig enteric nerve fibers.
Enteric neurons controlling various gut functions are prone to oxidative insults that might damage mitochondria (e.g., intestinal inflammation). To resume local energy supply, mitochondria need to be transported. We used MitoTracker dyes and confocal microscopy to investigate basic characteristics of mitochondrial transport in guinea pig myenteric neurites. During a 10-s observation of 1 mm nerve fiber, on average, three mitochondria were transported at an average speed of 0.41 +/- 0.02 microm/s. Movement patterns were clearly erratic, and velocities were independent of mitochondrial size. The velocity oscillated periodically ( approximately 6 s) but was not consistently affected by structures such as en route boutons, bifurcations, or stationary mitochondria. Also, mitochondria transported in opposite directions did not necessarily affect each others' mobility. Transport was blocked by microtubule disruption (100 microM colchicine), and destabilization (1 microM cytochalasin-D) or stabilization (10 microM phalloidin) of actin filaments, respectively, decreased (0.22 +/- 0.02 microm/s, P < 0.05) or increased (0.53 +/- 0.02 microm/s, P < 0.05) transport speed. Transport was inhibited by TTX (1 microM), and removal of extracellular Ca(2+) (plus 2 mM EGTA) had no effect. However, depletion of intracellular stores (thapsigargin) reduced (to 33%) and slowed the transport significantly (0.18 +/- 0.02 microm/s, P < 0.05), suggesting an important role for stored Ca(2+) in mitochondrial transport. Transport was also reduced (to 21%) by the mitochondrial uncoupler FCCP (1 microM) in a time-dependent fashion and slowed by oligomycin (10 microM). We conclude that mitochondrial transport is remarkably independent of structural nerve fiber properties. We also show that mitochondrial transport is TTX sensitive and speeds up by stabilizing actin and that functional Ca(2+) stores are required for efficient transport.
Department of Physiology and Cell Biology/352, University of Nevada, School of Medicine, Reno, Nevada 89557-0046, USA. tks@physio.unr.edu
Pieter
P
Vanden Berghe
Grant W
GW
Hennig
Terence K
TK
Smith
D000199:Actins / Q000378:metabolism; D000200:Action Potentials / Q000502:physiology; D000465:Algorithms; D000779:Anesthetics, Local / Q000494:pharmacology; D000818:Animals; D001693:Biological Transport, Active; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D017615:Enteric Nervous System / Q000166:cytology / Q000378:metabolism*; D005456:Fluorescent Dyes; D006168:Guinea Pigs; D006575:Heterocyclic Compounds, 3-Ring; D007091:Image Processing, Computer-Assisted; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D018613:Microscopy, Confocal; D008870:Microtubules / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism*; D009197:Myenteric Plexus / Q000166:cytology / Q000378:metabolism; D009412:Nerve Fibers / Q000378:metabolism*; D009840:Oligomycins / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology
D000199:Actins; D000779:Anesthetics, Local; D005456:Fluorescent Dyes; D006575:Heterocyclic Compounds, 3-Ring; D009840:Oligomycins; C068483:rhod-2; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D013779:Tetrodotoxin