Differential turnover of tyrosinated and detyrosinated microtubules.
Turnover of tyrosinated and detyrosinated microtubules ([Tyr]MTs and [Glu]MTs, respectively) was analyzed by the combined use of hapten-mediated immunocytochemistry and peptide-specific antibodies. Cells were microinjected with hapten-labeled tubulin and then processed for triple-label immunofluorescence to determine the pattern of incorporation of the injected subunits into [Tyr]- and [Glu]-MTs. Within 2 min of microinjection, hapten-labeled domains were present at the ends of virtually all [Tyr]MTs but were absent from most [Glu]MTs, demonstrating that [Tyr]MTs grew, whereas most [Glu]MTs did not. After 1 hr of incubation, all [Tyr]MTs analyzed were copolymers of endogenous and hapten-labeled subunits, indicating complete and rapid turnover of these MTs. However, the majority of [Glu]MTs were not hapten-labeled, indicating that they had not turned over. Even 16 hr after injection, cells that had not divided retained a small proportion of [Glu]MTs lacking hapten, implying that some had persisted for most of a cell generation. At mitosis, all MTs were hapten-labeled, indicating that the stable interphase [Glu]MTs had depolymerized. The results establish that the MT network is heterogeneous in its turnover rate, being composed of at least two populations: [Tyr]MTs that turn over rapidly and [Glu]MTs that turn over slowly.
Webster
D R
DR
Laboratory of Molecular Biology, University of Wisconsin, Madison, WI 53706.
Gundersen
G G
GG
Bulinski
J C
JC
Borisy
G G
GG
D000818:Animals; D002460:Cell Line; D002522:Chlorocebus aethiops; D005455:Fluorescent Antibody Technique; D046911:Macromolecular Substances; D008845:Microinjections; D008870:Microtubules / Q000378:metabolism*; D008938:Mitosis; D008941:Spindle Apparatus / Q000378:metabolism; D014404:Tubulin / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism*
D046911:Macromolecular Substances; D014404:Tubulin; D014443:Tyrosine