Evidence that estramustine binds MAP-1A to inhibit type IV collagenase secretion.
Estramustine is a novel anti-microtubule drug shown to bind MAP-1 and MAP-2 (microtubule-associated proteins) in vitro. In this paper we have shown that estramustine specifically binds MAP-1A in Du 145a cells, resulting in disruption of MAP-1A microtubules and inhibition of type IV collagenase secretion. Immunofluorescence studies revealed that at 30 microM levels estramustine blocked type IV collagenase secretion by partial disruption of the MAP-1A microtubule networks. Immunoprecipitation studies with polyclonal antibodies provided quantitative evidence that 30-60 microM estramustine blocked secretion of a 105 x 10(3) Mr type IV collagenase. Pulse-labeling experiments confirmed that the effect was not a result of inhibition of either protein synthesis or altered rates of type IV collagenase turnover. Finally, drug uptake studies with [3H]estramustine, scintillation counting and fluorography demonstrated that the principal target of the drug was MAP-1A. For the first time we have shown that the drug blocks secretion by binding MAP-1A and causing incomplete disruption of the microtubule networks.
Stearns
M E
ME
Medical College of Pennsylvania, Department of Pathology, Philadelphia 19129.
Wang
M
M
Sousa
O
O
D002460:Cell Line; D004961:Estramustine / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D006801:Humans; D003012:Microbial Collagenase / Q000378:metabolism*; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D011485:Protein Binding; D014316:Tritium
D008869:Microtubule-Associated Proteins; D014316:Tritium; D004961:Estramustine; D003012:Microbial Collagenase