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The calcium‐binding protein ALG‐2 promotes endoplasmic reticulum exit site localization and polymerization of Trk‐fused gene (TFG) protein
Author(s) -
Kanadome Takashi,
Shibata Hideki,
Kuwata Keiko,
Takahara Terunao,
Maki Masatoshi
Publication year - 2017
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/febs.13949
Subject(s) - endoplasmic reticulum , trk receptor , microbiology and biotechnology , gene , calcium , calcium binding protein , chemistry , binding protein , reticulum , biophysics , biochemistry , biology , receptor , neurotrophin , organic chemistry
Apoptosis‐linked gene 2 ( ALG ‐2), which is a gene product of PDCD 6 , is a 22‐ kD a Ca 2+ ‐binding protein. Accumulating evidence points to a role for ALG ‐2 as a Ca 2+ ‐responsive adaptor protein. On binding to Ca 2+ , ALG ‐2 undergoes a conformational change that facilitates its interaction with various proteins. It also forms a homodimer and heterodimer with peflin, a paralog of ALG ‐2. However, the differences in cellular roles for the ALG ‐2 homodimer and ALG ‐2/peflin heterodimer are unclear. In the present study, we found that Trk‐fused gene ( TFG ) protein interacted with the ALG ‐2 homodimer. Immunostaining analysis revealed that TFG and ALG ‐2 partially overlapped at endoplasmic reticulum exit sites ( ERES ), a platform for COPII ‐mediated protein transport from the endoplasmic reticulum. Time‐lapse live‐cell imaging demonstrated that both green fluorescent protein‐fused TFG and mC herry‐fused ALG ‐2 are recruited to ERES after thapsigargin treatment, which raises intracellular Ca 2+ levels. Furthermore, overexpression of ALG ‐2 induced the accumulation of TFG at ERES . TFG has an ALG ‐2‐binding motif and deletion of the motif decreased TFG binding to ALG ‐2 and shortened its half‐life at ERES , suggesting a critical role for ALG ‐2 in retaining TFG at ERES . We also demonstrated, by in vitro cross‐linking assays, that ALG ‐2 promoted the polymerization of TFG in a Ca 2+ ‐dependent manner. Collectively, the results suggest that ALG ‐2 acts as a Ca 2+ ‐sensitive adaptor to concentrate and polymerize TFG at ERES , supporting a potential role for ALG ‐2 in COPII ‐dependent trafficking from the endoplasmic reticulum.