CKAP4 Regulates Cell Migration via the Interaction with and Recycling of Integrin

ABSTRACT

Cytoskeleton-associated protein 4 (CKAP4) is an endoplasmic reticulum protein that is also present in the cell surface membrane, where it acts as a receptor for Dickkopf1 (DKK1). In this study, we found that CKAP4 interacts with β1 integrin and controls the recycling of α5β1 integrin independently of DKK1. In S2-CP8 cells, knockdown of CKAP4 but not DKK1 enlarged the size of cell adhesion sites and enhanced cell adhesion to fibronectin, resulting in decreased cell migration. When CKAP4 was depleted, the levels of α5 but not β1 integrin were increased in the cell surface membrane. A similar phenotype was observed in other cells expressing low levels of DKK1. In S2-CP8 cells, α5 integrin was trafficked with β1 integrin and CKAP4 to the lysosome or recycled with β1 integrin. In CKAP4-depleted cells, the internalization of α5β1 integrin was unchanged, but its recycling was upregulated. Knockdown of sorting nexin 17 (SNX17), a mediator of integrin recycling, abrogated the increased α5 integrin levels caused by CKAP4 knockdown. CKAP4 bound to SNX17, and its knockdown enhanced the recruitment of α5β1 integrin to SNX17. These results suggest that CKAP4 suppresses the recycling of α5β1 integrin and coordinates cell adhesion sites and migration independently of DKK1.

KEYWORDS:

• CKAP4
• SNX17
• cell adhesion
• fibronectin
• integrins
• recycling

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SUPPLEMENTAL MATERIAL

Supplemental material for this article may be found at https://doi.org/10.1128/MCB.00073-19.

ACKNOWLEDGMENTS

We thank the Center of Medical Research and Education, Graduate School of Medicine, Osaka University, for in-gel digestion and LC-MS/MS analysis and S. Tsukita, M. Hatakeyama, Y. Matsuura, T. Tanaka, K. Matsumoto, and A. Shintani for donating cells. We also thank J. Kikuta and M. Ishii for their assistance in the observation of cell migration and H. Kimura and R. Sada for critical reading of the manuscript.

This work was supported by Grants-in-Aid for Scientific Research (S) to A.K. (2016-2020) (no. 16H06374) and Grants-in-Aid for Scientific Research on Innovative Areas, Organelle Zone, to A.K. (2018-2019) (no. 18H04861).

Y.O. performed most of the experiments. K.F. performed some of the experiments, including the quantitative analysis of colocalization. K.F. and A.K. designed the experiments, interpreted the results, and coauthored the manuscript.

We declare no conflicts of interest.