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First published online 23 April 2008
doi: 10.1242/dev.017103

Development 135, 1923-1933 (2008)
Published by The Company of Biologists 2008
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The gradient of Gurken, a long-range morphogen, is directly regulated by Cbl-mediated endocytosis

Wei-Ling Chang1, Willisa Liou2, Hsiao-Chung Pen1, He-Yen Chou1, Yu-Wei Chang1, Wei-How Li1, Wei Chiang1 and Li-Mei Pai1,*

1 Department of Biochemistry, Chang Gung University, Tao-Yuan, 333, Taiwan.
2 Department of Anatomy, Chang Gung University, Tao-Yuan, 333, Taiwan.

* Author for correspondence (e-mail: pai{at}mail.cgu.edu.tw)

Accepted 26 March 2008

The asymmetric localization of gurken mRNA and post-translational sorting mechanisms are responsible for the polar distribution of Gurken protein in Drosophila. However, endocytosis of Egfr, the receptor for Gurken in the follicle cells, also plays a role in shaping the extracellular gradient of the Gurken morphogen. Previously, we have found that mutation in the Cbl gene caused elevated Egfr signaling along the dorsoventral axis, and resulted in dorsalization phenotypes in embryos and egg shells. Here, we report that overexpression of the Cbl long isoform significantly changed Gurken distribution. Using an HRP-Gurken fusion protein, we demonstrate that internalization of the Gurken-Egfr complex depends on the activity of Cbl. Increased levels of CblL promote the internalization of this complex, leading to the reduction of free ligands. The Gurken-Egfr complex trafficks through the Rab5/Rab7 associated endocytic pathway to the lysosomal degradation compartment for signaling termination. We observe endocytic Gurken not only in the dorsal but also in the ventral follicle cells, which is, to our knowledge, the first visualization of Gurken on the ventral side of egg chambers. Our results show that Gurken travels towards the lateral/posterior of the egg chamber in the absence of Cbl, suggesting that Cbl actively regulates Gurken distribution through promoting endocytosis and subsequent degradation.

Key words: Gurken, Egfr, Cbl, Morphogen gradient, Endocytosis, Drosophila


Related articles in Development:

Endocytosis: shaping the Gurken gradient

Development 2008 135: e1104. [Full Text]  





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