title: The intracellular transport and secretion of calumenin-1/2 in living cells.
abstract: Calumenin isoforms 1 and 2 (calu-1/2), encoded by the CALU gene, belong to the CREC protein family. Calu-1/2 proteins are secreted into the extracellular space, but the secretory process and regulatory mechanism are largely unknown. Here, using a time-lapse imaging system, we visualized the intracellular transport and secretory process of calu-1/2-EGFP after their translocation into the ER lumen. Interestingly, we observed that an abundance of calu-1/2-EGFP accumulated in cellular processes before being released into the extracellular space, while only part of calu-1/2-EGFP proteins were secreted directly after attaching to the cell periphery. Moreover, we found the secretion of calu-1/2-EGFP required microtubule integrity, and that calu-1/2-EGFP-containing vesicles were transported by the motor proteins Kif5b and cytoplasmic dynein. Finally, we determined the export signal of calu-1/2-EGFP (amino acid positions 20-46) and provided evidence that the asparagine at site 131 was indispensable for calu-1/2-EGFP stabilization. Taken together, we provide a detailed picture of the intracellular transport of calu-1/2-EGFP, which facilitates our understanding of the secretory mechanism of calu-1/2.
authors.affiliation: State Key Laboratory of Bio-membrane and Membrane Bio-engineering and Key Laboratory of Cell Proliferation and Differentiation of the Ministry of Education, College of Life Sciences, Peking University, Beijing, China.
authors.forename: Qiao
authors.initials: Q
authors.lastname: Wang
authors.forename: Hui
authors.initials: H
authors.lastname: Feng
authors.forename: Pengli
authors.initials: P
authors.lastname: Zheng
authors.forename: Birong
authors.initials: B
authors.lastname: Shen
authors.forename: Liang
authors.initials: L
authors.lastname: Chen
authors.forename: Lin
authors.initials: L
authors.lastname: Liu
authors.forename: Xiao
authors.initials: X
authors.lastname: Liu
authors.forename: Qingsong
authors.initials: Q
authors.lastname: Hao
authors.forename: Shunchang
authors.initials: S
authors.lastname: Wang
authors.forename: Jianguo
authors.initials: J
authors.lastname: Chen
authors.forename: Junlin
authors.initials: J
authors.lastname: Teng
mesh_terms: D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D004398:Dyneins / Q000235:genetics / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D047468:Immunoprecipitation; D016547:Kinesins / Q000235:genetics / Q000378:metabolism; D008856:Microscopy, Fluorescence; D011485:Protein Binding / Q000235:genetics / Q000502:physiology; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism*; D055550:Protein Stability; D021381:Protein Transport / Q000235:genetics / Q000502:physiology; D034622:RNA Interference
chemical_list: C510527:CALU protein, human; D002135:Calcium-Binding Proteins; C488101:KIF5B protein, human; D020033:Protein Isoforms; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D004398:Dyneins; D016547:Kinesins