Fig. 1.

Actin filament depolymerization has no effect on the decrease in the cytosolic ATP level induced by blockade of ATP production in forebrain neurons. (A) Schematic of actin filament polymerization and depolymerization, and the effects of jasplakinolkide and latrunculin-A on actin filament dynamics. Actin monomers (yellow) undergo ATP loading in the cytoplasm priming them for polymerization onto the barbed end of filaments. The ATP is hydrolyzed to ADP+Pi while the actin monomer (blue) is in residence within the filament. ADP actin is then released from the pointed end of the filament and reloaded with ATP. Latrunuclin binds actin monomers and prevents their polymerization (1) and also accelerates the release of actin monomers from filaments (2). Jasplakinolide binds to actin within filaments and inhibits its release, effectively stabilizing the filaments. This leads to the incorporation of the majority of soluble actin into stable filaments when polymerization remains unaltered. (B) A combined suppression of oxidative phosphorylation using antimycin-A (AA) and glycolysis using GIM for 30 min decreases the cellular ATP level as assessed using a luciferase-based assay. A 10 min pretreatment with latrunculin-A does not impact the decrease in the cellular ATP level induced by GIM+AA. Error bars are mean±s.e.m. n=5 for all groups. P-values calculated with an unpaired one-tailed Welch t-test. (C) Representative examples from three cultures per group of the distal axons of forebrain neurons stained to reveal actin filaments (F-actin) and tubulin. The 10 min pre-treatment with latrunculin-A depolymerizes actin filaments and the effect persists until 40 min of treatment reflective of the entire time course of the experiment in B.