Kinesin localizes to the trans-Golgi network regardless of microtubule organization.

Knowledge of the mechanisms of intracellular membrane trafficking is critical for understanding cell function. Here, the microtubule motor kinesin is localized to the Sertoli cell trans-Golgi network with the SUK4 kinesin monoclonal antibody. Using immunoelectron and immunofluorescence microscopy, kinesin was shown to localize to the trans-Golgi network in primary Sertoli cell cultures. Kinesin immunostaining was not observed in brefeldin A-induced trans-Golgi network-derived membrane tubules and remained associated with trans-Golgi network remnants. Despite dramatic differences in microtubule organization between Sertoli cells in vivo and in vitro, kinesin immunostaining was consistently associated with the trans-Golgi network. In cryosections of control testis and testis treated with colchicine to disrupt microtubules, kinesin immunostaining was juxtaposed with immunostaining for a Golgi cisternal protein; however, brefeldin A exposure partitioned the kinesin immunostaining from the Golgi cisternal protein, indicating that kinesin was associated with the trans-Golgi network of Sertoli cells in vivo. These results are discussed in relation to known Golgi-associated microtubule-dependent transport events in other cell types and suggest that kinesin functions locally at the Sertoli cell trans-Golgi network.