Submitted on May 22, 2008
Revised on July 2, 2008
Accepted on July 3, 2008
Fluorescence-topographic NSOM directly visualizes peak-valley polarities of GM1/GM3 rafts in membrane fluctuations
Yong Chen, Jie Qin, and Zheng W. Chen
University of Illinois College of Medicine, Chicago, IL 60612
Corresponding Author: zchen{at}uic.edu
Simultaneous fluorescence-topographic nanoscale imaging of cell-surface molecules in the context of membrane ultra-structures has not been reported. Here, NSOM-based direct fluorescence-topographic imaging indicated that GM3 rafts/nanodomains (190.0±49.8 nm ranging 84.5 - 365.0 nm) were localized predominantly on the peaks of microvillus-like protrusions in the apical membrane of GM3+ MDCK cells, whereas GM1 rafts/nanodomains (159.5±63.8 nm ranging 42 - 360 nm) were distributed mainly on the slops of protrusions or the valleys between protrusions in the plasma membranes of GM1+ MDCK cells. The data demonstrated that gangliosides polarized not only in a well-known apical-basolateral manner but also in the more microscopic peak-valley manner, implicating unique distribution of GM1 or GM3 in cell-surface fluctuations on the apical membrane of polarized cells. The peak-valley polarities of gangliosides also implicated their different functions relevant to lipid rafts, microvilli, or cellular processes. Importantly, our study demonstrated for the first time that the NSOM-based direct fluorescence-topographic imaging is unique and powerful for elucidating nanoscale distribution of specific cell-surface molecules in membrane fluctuations.
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