The neurite-initiating effect of microbial extracellular glycolipids in PC12 cells

The effects of several kinds of microbial extracellular glycolipids on neur ite initiation in PC12 cells were examined. Addition of mannosylerythritol lipid-A (MEL-A), MEL-B, and sophorose lipid (SL) to PC12 cells caused signi ficant neurite outgrowth. Other glycolipids, such as polyol lipid (PL), rha mnose lipid (RL), succinoyl trehalose lipid-A (STL-A) and STL-B caused no n eurite-initiation. MEL-A increased acetylcholine esterase (AChE) activity t o an extent similar to nerve growth factor (NGF). However, MEL-A induced on e or two long neurites from the cell body, while NGF induced many neurites. In addition, MEL-A-induced differentiation was transient, and after 48 h, percentage of cells with neurites started to decrease in contrast to neuron s induced by NGF, which occurred in a time-dependent manner. MEL-A could in duce neurite outgrowth after treatment of PC12 cells with an anti-NGF recep tor antibody that obstructed NGF action. These results indicate that MEL-A and NGF induce differentiation of PC12 cells through different mechanisms.