title: Tau-isoform dependent enhancement of taxol mobility through microtubules.
abstract: Tau, a family of microtubule-associated proteins (MAPs), stabilizes microtubules (MTs) and regulates their dynamics. Tau isoforms regulate MT dynamic instability differently: 3-repeat tau is less effective than 4-repeat tau at suppressing the disassembly of MTs. Here, we report another tau-isoform-dependent phenomenon, revealed by fluorescence recovery after photobleaching measurements on a BODIPY-conjugated taxol bound to MTs. Saturating levels of recombinant full-length 3-repeat and 4-repeat tau both cause taxol mobility to be remarkably sensitive to taxol concentration. However, 3-repeat tau induces 2.5-fold faster recovery ( approximately 450s) at low taxol concentrations ( approximately 100 nM) than 4-repeat tau ( approximately 1000 s), indicating that 3-repeat tau decreases the probability of taxol rebinding to its site in the MT lumen. Finding no tau-induced change in the MT-binding affinity of taxol, we conclude that 3-repeat tau either competes for the taxol binding site with an affinity of approximately 1 microM or alters the MT structure so as to facilitate the passage of taxol through pores in the MT wall.
authors.affiliation: Physics Department, Korea Advanced Institute of Science and Technology, Daejeon 305-701, Republic of Korea. phj78@kaist.ac.kr
authors.forename: Hyunjoo
authors.initials: H
authors.lastname: Park
authors.forename: Mahnwon
authors.initials: M
authors.lastname: Kim
authors.forename: Deborah K
authors.initials: DK
authors.lastname: Fygenson
mesh_terms: D001692:Biological Transport; D001896:Boron Compounds / Q000494:pharmacology*; D036681:Fluorescence Recovery After Photobleaching; D006801:Humans; D007700:Kinetics; D046529:Microscopy, Electron, Transmission; D008870:Microtubules / Q000737:chemistry*; D017239:Paclitaxel / Q000737:chemistry / Q000494:pharmacology*; D011485:Protein Binding; D020033:Protein Isoforms; D013050:Spectrometry, Fluorescence / Q000379:methods; D050257:Tubulin Modulators / Q000494:pharmacology; D016875:tau Proteins / Q000737:chemistry* / Q000378:metabolism*
chemical_list: C095489:4,4-difluoro-4-bora-3a,4a-diaza-s-indacene; D001896:Boron Compounds; D020033:Protein Isoforms; D050257:Tubulin Modulators; D016875:tau Proteins; D017239:Paclitaxel