Distribution of acetylated α‐tubulin in retina and in in vitro—assembled microtubules

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Abstract
We have used the mouse monoclonal antibody 6‐11B‐1, specific for acetylated α‐tubulin, to determine the distribution of acetylated α‐tubulin in in vitro–assembled microtubules and retinal tissue. Analysis by immunoblots revealed that microtubules assembled from bovine brain extracts contain both acetylated and nonacetylated α‐tubulin. Immunofluorescence, using 6‐11B‐1 and antitubulin B‐5‐1‐2, a monoclonal antibody specific for α‐tubulin, demonstrated the colocalization of both α‐tubulin species in neurons of the retina and that acetylated microtubules are relatively abundant in neurons. However, analysis at higher resolution revealed that rod photoreceptors contain spatially distinct microtubule arrays which differ in content of acetylated α‐tubulin and differ in stability. Acetylated microtubules which composed those of the rod outer segment and connecting cilium were resistant to depolymerization in nocodazole or colchicine. In contrast, the nonacetylated microtubules which composed those of the rod‐inner segment were depolymerized in nocodazole or colchicine. Therefore, these acetylated microtubules are more resistant to depolymerization than non‐acetylated microtubules.