Effect of estramustine phosphate on the assembly of trypsin-treated microtubules and microtubules reconstituted from purified tubulin with either tau, MAP2, or the tubulin-binding fragment of MAP2.
Estramustine phosphate, an estradiol nitrogen-mustard derivative is a microtubule-associated protein (MAP)-binding microtubule inhibitor, used in the therapy of prostatic carcinoma. It was found to inhibit assembly and to induce disassembly of microtubules reconstituted from phosphocellulose-purified tubulin with either tau, microtubule-associated protein 2, or chymotrypsin-digested microtubule-associated protein 2. Estramustine phosphate also inhibited assembly of trypsin-treated microtubules, completely depleted of high-molecular-weight microtubule-associated proteins, but with their microtubule-binding fragment present. In all cases estramustine phosphate induced disassembly to about 50%, at a concentration of approximately 100 microM, at similar protein concentrations. However, estramustine phosphate did not affect dimethyl sulfoxide-induced assembly of phosphocellulose-purified tubulin. Estramustine phosphate is a reversible inhibitor, as the nonionic detergent Triton X-100 was found to counteract the inhibition in a concentration-dependent manner. The reversibility was nondisruptive, as Triton X-100 itself did not affect microtubule assembly, microtubule protein composition, or morphology. This new reversible MAPs-dependent inhibitor estramustine phosphate affects the tubulin assembly, induced by tau, as well as by the small tubulin-binding part of MAP2 with the same concentration dependency. This indicates that tau and the tubulin-binding part of MAP2, in addition to their assembly promoting functions also have binding site(s) for estramustine phosphate in common.
D001665:Binding Sites; D004961:Estramustine / Q000378:metabolism / Q000494:pharmacology*; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D008870:Microtubules / Q000187:drug effects* / Q000378:metabolism; D009588:Nitrogen Mustard Compounds / Q000494:pharmacology*; D017830:Octoxynol; D010446:Peptide Fragments / Q000378:metabolism*; D011092:Polyethylene Glycols / Q000494:pharmacology; D014357:Trypsin / Q000494:pharmacology*; D014404:Tubulin / Q000378:metabolism*; D016875:tau Proteins
D008869:Microtubule-Associated Proteins; D009588:Nitrogen Mustard Compounds; D010446:Peptide Fragments; D014404:Tubulin; D016875:tau Proteins; D004961:Estramustine; D011092:Polyethylene Glycols; D017830:Octoxynol; D014357:Trypsin