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Biochem Biophys Res Commun. 2001 Jul 20;285(3):845-53.

Matrix vesicles and media vesicles as nonclassical pathways for the secretion of m-Calpain from MC3T3-E1 cells.

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Department of Orthopedic Surgery, Faculty of Medicine, Kyoto University, 54 Shogoin Kawahara-cho, Sakyoku, Kyoto 606-8507, Japan.


Calpain was generally believed to exist and function only in the cytoplasm. However, m-calpain has now been detected in the extracellular spaces of some kinds of tissue. In this study, we demonstrated the existence of m-calpain in the medium surrounding MC3T3-E1 cultures, and its activity by zymography. At the same time, the amount of lactate dehydrogenase in medium of MC3T3-E1 culture was extremely low compared with other cell cultures, suggesting that m-calpain found in the culture medium of MC3T3-E1 cells originated mainly from active secretion. Moreover, the secretion of m-calpain was not blocked by brefeldin A, implying that m-calpain may be secreted by a nonclassical pathway. Recently, MC3T3-E1 has been reported to produce matrix vesicles and media vesicles, and we demonstrated m-calpain in these vesicles produced by MC3T3-E1 cultures. We therefore concluded that these vesicles are partly responsible for the secretion of m-calpain into the culture medium of MC3T3-E1 cells.

[Indexed for MEDLINE]

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