CRACR2a is a calcium-activated dynein adaptor protein that regulates endocytic traffic

J Cell Biol. 2019 May 6;218(5):1619-1633. doi: 10.1083/jcb.201806097.

Yuxiao Wang ¹ ², Walter Huynh ¹ ², Taylor D Skokan ¹ ², Wen Lu ³, Arthur Weiss ² ³, Ronald D Vale ⁴ ²

Affiliations

1 Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA.
2 Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA.
3 Division of Rheumatology, Rosalind Russell and Ephraim P. Engleman Arthritis Research Center, Department of Medicine, University of California, San Francisco, San Francisco, CA.
4 Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA ron.vale@ucsf.edu.

PMID: 30814157 DOI: 10.1083/jcb.201806097

Abstract

Cytoplasmic dynein is a minus end-directed microtubule motor that transports intracellular cargoes. Transport is initiated by coiled-coil adaptors that (a) join dynein and its cofactor dynactin into a motile complex and (b) interact with a cargo-bound receptor, which is frequently a Rab GTPase on an organelle. Here, we report two novel dynein adaptors, CRACR2a and Rab45, that have a coiled-coil adaptor domain, a pair of EF-hands, and a Rab GTPase fused into a single polypeptide. CRACR2a-mediated, but not Rab45-mediated, dynein motility is activated by calcium in vitro. In Jurkat T cells, elevation of intracellular calcium activates CRACR2a-mediated dynein transport. We further found that T cell receptor activation induces the formation of CRACR2a puncta at the plasma membrane, which initially associate with the actin cortex and subsequently detach and travel along microtubules, suggestive of an endocytic process. These results provide the first examples of Rab GTPases that directly act as dynein adaptors and implicate CRACR2a-dynein in calcium-regulated endocytic trafficking.

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