AMP-activated protein kinase mediates activity-dependent axon branching by recruiting mitochondria to axon.
During development, axons are guided to their target areas and provide local branching. Spatiotemporal regulation of axon branching is crucial for the establishment of functional connections between appropriate pre- and postsynaptic neurons. Common understanding has been that neuronal activity contributes to the proper axon branching; however, intracellular mechanisms that underlie activity-dependent axon branching remain elusive. Here, we show, using primary cultures of the dentate granule cells, that neuronal depolarization-induced rebalance of mitochondrial motility between anterograde versus retrograde transport underlies the proper formation of axonal branches. We found that the depolarization-induced branch formation was blocked by the uncoupler p-trifluoromethoxyphenylhydrazone, which suggests that mitochondria-derived ATP mediates the observed phenomena. Real-time analysis of mitochondrial movement defined the molecular mechanisms by showing that the pharmacological activation of AMP-activated protein kinase (AMPK) after depolarization increased anterograde transport of mitochondria into axons. Simultaneous imaging of axonal morphology and mitochondrial distribution revealed that mitochondrial localization preceded the emergence of axonal branches. Moreover, the higher probability of mitochondrial localization was correlated with the longer lifetime of axon branches. We qualitatively confirmed that neuronal ATP levels decreased immediately after depolarization and found that the phosphorylated form of AMPK was increased. Thus, this study identifies a novel role for AMPK in the transport of axonal mitochondria that underlie the neuronal activity-dependent formation of axon branches.
Laboratory of Chemical Pharmacology Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, 113-0033, Japan.
Kentaro
K
Tao
Norio
N
Matsuki
Ryuta
R
Koyama
D055372:AMP-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D000620:Aminoimidazole Carboxamide / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D001370:Axonal Transport / Q000187:drug effects; D001369:Axons / Q000187:drug effects / Q000378:metabolism*; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D002478:Cells, Cultured; D018891:Dentate Gyrus / Q000166:cytology; D004305:Dose-Response Relationship, Drug; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D020439:Growth Cones; D018398:Homeodomain Proteins / Q000378:metabolism; D007004:Hypoglycemic Agents / Q000494:pharmacology; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D009474:Neurons / Q000166:cytology* / Q000187:drug effects; D011189:Potassium Chloride / Q000494:pharmacology; D061209:Proton Ionophores / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012265:Ribonucleotides / Q000494:pharmacology; D025521:Tumor Suppressor Proteins / Q000378:metabolism; D000098551:Prospero-Related Homeobox 1 Protein
D018398:Homeodomain Proteins; D007004:Hypoglycemic Agents; D061209:Proton Ionophores; D012265:Ribonucleotides; D025521:Tumor Suppressor Proteins; D000098551:Prospero-Related Homeobox 1 Protein; D049452:Green Fluorescent Proteins; D000620:Aminoimidazole Carboxamide; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D011189:Potassium Chloride; D055372:AMP-Activated Protein Kinases; C031143:AICA ribonucleotide
AMP-activated protein kinase; axon branching; axonal transport; granule cell; mitochondria