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Birgitte Mønster Christensen

Human calumenin localizes to the secretory pathway and is secreted to the medium.

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  • Institut for Medicinsk Biokemi
  • Klinisk Institut
  • Anatomisk Institut
Calumenin belongs to a family of multiple EF-hand proteins that include reticulocalbin, ERC-55, and Cab45. Reticulocalbin and ERC-55 localize to the ER due to a C-terminal HDEL retrieval signal. Cab45 contains a HEEF C-terminal sequence and is localized to the Golgi apparatus. The murine homologue of calumenin is reported to be present in the ER due to a C-terminal HDEF retrieval signal. The human homologue differs from the murine at 7 amino acid positions but the HDEF signal is conserved. However, in the cultured human cell lines, HaCaT keratinocytes, normal and transformed MRC-5 fibroblasts, as well as in transfected COS-1 cells, human calumenin could be demonstrated in the ER as well as in the Golgi complex. Especially in MRC-5 cells, a certain heterogeneity was observed, with some of the cells having calumenin localized solely to the ER while in other cells calumenin could be demonstrated in the ER as well as in the Golgi complex. Immunoelectron microscopy of placental syncytiotrophoblast cells showed that a substantial fraction of calumenin is localized in close association with the ER membrane. In addition, the protein may be recovered from the medium of cultured cells in an endoglycosidase H-resistant form, suggesting that the glycosylated protein has been further modified in the Golgi apparatus and secreted to the medium.
Udgivelsesdato: 1999-May-1
OriginalsprogEngelsk
TidsskriftExperimental Cell Research
Vol/bind248
Nummer2
Sider (fra-til)473-81
Antal sider8
ISSN0014-4827
DOI
StatusUdgivet - 1999

Bibliografisk note

Copyright 1999 Academic Press.

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