Differential distribution of calpain in human lymphoid cells.
Calpain, a calcium-activated neutral proteinase, is ubiquitously present in human tissues. To determine if lymphoid cells implicated in pathogenesis of demyelination may harbor calpain in a functionally active form, we determined both muCalpain and mCalpain activities in human lymphoid cell lines. DEAE-cellulose and phenylsepharose column chromatography were used to isolate the enzyme from the natural inhibitor, calpastatin. Lymphocytic lines (CCRF-CEM, MOLT-3, MOLT-4, M.R.) showed predominance of muCalpain (55-80%) whereas the monocytic line (U-937) showed predominance of mCalpain (77%). Proportion and subcellular distribution of both isoforms varied among cell lines. Calpains isolated from U-937 cells degraded myelin basic protein. These results indicate that human lymphoid cells harbor functionally active calpain that can degrade myelin components in vitro. The study suggests a degradative role for calpain in demyelinating diseases.
Deshpande
R V
RV
Department of Microbiology and Immunology, Medical University of South Carolina, Charleston 29425.
Goust
J M
JM
Banik
N L
NL
D002135:Calcium-Binding Proteins / Q000032:analysis; D002154:Calpain / Q000032:analysis* / Q000378:metabolism; D002462:Cell Membrane / Q000201:enzymology; D003600:Cytosol / Q000201:enzymology; D006801:Humans; D008214:Lymphocytes / Q000201:enzymology* / Q000648:ultrastructure; D004676:Myelin Basic Protein / Q000378:metabolism; D009186:Myelin Sheath / Q000378:metabolism; D014407:Tumor Cells, Cultured
D002135:Calcium-Binding Proteins; D004676:Myelin Basic Protein; C033668:calpastatin; D002154:Calpain