We used the technique of single particle tracking (SPT) with high tempo-spatial resolution to efficiently explore the route and mechanism for the transport Of alpha(1A)-adrenergic receptor (alpha(1A)-AR) in real time in living cells. We found that the initial transport Of alpha(1A)-AR in cells depended on actin filaments with the velocity of 0.2 mu m/s and exhibited discrete 33-nm steps. It was noted that the step size, the rate constant, and the velocities were in accordance with the character of single myosin in vitro, implying that while transporting each endosome myosins did not work in the "tug-of-war" mode and that they did not adopt the strategy to boost up transporting speed by working coordinately. These results provided insight into the mechanism of GPCR transport ill vivo. (c) 2006 Elsevier Inc. All rights reserved.