Various N-terminal tags have often been used to identify the functions and localization of Rab small GTPases, but their impact on Rab proteins themselves has been poorly investigated. Here, we used a knockout (KO)–rescue approach to systematically evaluate the effect of N-terminal tagging of two Rabs, Rab10 and Rab27A, on RAB10-KO HeLa cells and Rab27A-deficient melanocytes (melan-ash cells), respectively. The results showed that all of the N-terminal-tagged Rab27A proteins mediated actin-based melanosome transport in the melan-ash cells, but none of the N-terminal-tagged Rab10 proteins fully rescued the defect in tubular endosome formation in RAB10-KO cells. Although the N-terminal-tagged Rab10 proteins had the ability to localize tubular endosomes in wild-type HeLa cells, they sometimes exhibited a dominant-negative effect on tubular endosome formation. We also found that a conserved lysine residue at amino acid position 3 (K3) in the Rab10 proteins of different species is required for tubular endosome formation. Thus, it will be important to determine whether other Rab isoforms with N-terminal tags behave similarly to their corresponding untagged isoforms by performing appropriate KO–rescue experiments in future studies.

Author contributions

Conceptualization: R.H., M.F.; Funding acquisition: M.F.; Investigation: R.H., A.S.; Supervision: M.F.; Writing – original draft: R.H., M.F.; Writing – review & editing: R.H., A.S., M.F.

Funding

This work was supported in part by Grant-in-Aid for Scientific Research(B) from the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan (grant number 22H02613 to M.F.), and by a grant from the Naito Foundation (to M.F.).

Data availability

All relevant data can be found within the article and its supplementary information.

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