Changes in the pattern and amount of microtubule acetylation in response to ATP depletion

Previous research has shown that cells depleted of ATP develop microtubules (MTs) that are stable in the presence of microtubule‐depolymerizing drugs. Since it is known that stable MTs display more post‐translational modifications, we investigated whether MTs in ATP‐depleted cells become acetylated. C3H10T1/2 mouse embryo fibroblasts were treated for 2 hours with 20 mM sodium azide and 10 mM 2‐deoxyglucose (Az‐2DG) to stabilize the MTs. Analysis by immunofluorescence microscopy revealed an increase in MT acetylation in response to ATP depletion and a change in the pattern of acetylation. Control cells showed discreet patches of acetylation on some but not all MTs. In contrast, ATP‐depleted cells more frequently showed continuous staining for acetylated tubulin along their lengths. This change in acetylation was readily reversed. When cells were returned to normal medium and allowed to recover from Az‐2DG treatment for 30, 60 and 120 minutes, a clear decrease in acetylation was seen within 30 minutes. By 120 minutes, the pattern and amount of acetylation appeared identical to control untreated cells. Little is known about the enzymes responsible for tubulin acetylation. Our results suggest that the tubulin acetylation enzymes are not ATP‐dependent and tubulin deacetylation occurs rapidly once ATP levels return to normal. Support from a Merck/AAAS grant to Union College is gratefully acknowledged.