Characterization of GLUT4-containing vesicles in 3T3-L1 adipocytes by total internal reflection fluorescence microscopy |
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Authors: | Yan Wang JinZhong Zhang Yu Chen Li Jiang Wei Ji Tao Xu |
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Institution: | (1) National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China;(2) Graduate University of Chinese Academy of Sciences, Beijing, 100049, China |
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Abstract: | Insulin-responsive GLUT4 (glucose transporter 4) translocation plays a major role in regulating glucose uptake in adipose
tissue and muscle. Whether or not there is a specialized secretory GSV (GLUT4 storage vesicle) pool, and more importantly
how GSVs are translocated to the PM (plasma membrane) under insulin stimulation is still under debate. In the present study,
we systematically analyzed the dynamics of a large number of single GLUT4-containing vesicles in 3T3-L1 adipocytes by TIRFM
(total internal reflection fluorescence microscopy). We found that GLUT4-containing vesicles can be classified into three
groups according to their mobility, namely vertical, stable, and lateral GLUT4-containing vesicles. Among these groups, vertical
GLUT4-containing vesicles exclude transferrin receptors and move towards the PM specifically in response to insulin stimulation,
while stable and lateral GLUT4-containing vesicles contain transferrin receptors and show no insulin responsiveness. These
data demonstrate that vertical GLUT4-containing vesicles correspond to specialized secretory GSVs, which approach the PM directly
and bypass the constitutive recycling pathway.
Contributed equally to this work
Supported by the National Natural Science Foundation of China (Grant Nos. 30470448 and 30130230), the National key Basic Research
Program of China (Grant No. 2004CB720000), the Knowledge Innovative Program of The Chinese Academy of Sciences (Grant Nos.
KSCX2-SW-224 and Y2004018), the Li Foundation and the Sinogerman Scientific Center. |
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Keywords: | GLUT4 IRAP-pHluorin GSV transferring TIRFM |
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