Function of the Ryk intracellular domain in C. elegans vulval development

Authors

  • Woon Cheng Poh,

    1. Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
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  • Yanqing Shen,

    1. Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
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  • Takao Inoue

    Corresponding author
    1. Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
    • Correspondence to: Takao Inoue, Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 117597. E-mail: bchti@nus.edu.sg

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Abstract

Background: Ryk is a subfamily of receptor tyrosine kinases, which along with Frizzled and Ror, function as Wnt receptors. Vertebrate Ryk intracellular domain (ICD) is released from the cell membrane by a proteolytic cleavage in the transmembrane region and localizes to the nucleus. In C. elegans, Ryk is encoded by the lin-18 gene and regulates the polarity of the P7.p vulval cell. Results: Based on Western blots, we were unable to detect the presence of the cleaved LIN-18 ICD fragment. Functional assays found that LIN-18 intracellular domain is not absolutely required for LIN-18 function, consistent with previous results. However, overexpression of the LIN-18 intracellular domain fragment (LIN-18ICD) weakly enhanced the phenotype of lin-18 loss-of-function mutants. Furthermore, this activity was specific to the serine-rich juxtamembrane region. We also found that the nuclear localization of LIN-18ICD fragment can be regulated by Wnt pathway components including CAM-1/Ror, and by PAR-5/14-3-3. Conclusions: Release of LIN-18ICD by cleavage at the membrane is not the main mechanism of LIN-18 signaling in vulval cells. However, our results suggest that LIN-18 intracellular domain interacts with Wnt pathway components and a 14-3-3 protein and likely plays a minor role in LIN-18 signaling. Developmental Dynamics 243:1074–1085, 2014. © 2014 Wiley Periodicals, Inc.

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