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Cystatin F is a cysteine peptidase inhibitor recently discov-ered in haematopoietic cells by cDNA cloning. To further investigate the expression,distribution and properties of the native human inhibitor the promyeloid cell line U937 has beenstudied.The cells expressedrelatively largequantities of cystatin F,which was found both secreted and intracellu-larly. The intracellular levels were unusually high for a secreted cystatin ( 25% of the cystatin F in 2- or 4-day culture medium). | Eur. J. Biochem. 269 5502-5511 2002 FEBS 2002 doi 10.1046 j.1432-1033.2002.03252.x Regulated expression and intracellular localization of cystatin F in human U937 cells Carl-Michael Nathanson1 Johan Wasselius2 Hanna Wallin1 and Magnus Abrahamson1 1 Department of Clinical Chemistry Institute of Laboratory Medicine and department of Ophtalmology University of Lund University Hospital Lund Sweden Cystatin F is a cysteine peptidase inhibitor recently discovered in haematopoietic cells by cDNA cloning. To further investigate the expression distribution and propetiies ol the native human inhibitor the promyeloid cell line U937 has been studied. The cells expressed relatively large quantities of cystatin F whihh was omidl both serreted and trceellu-larly. The intracellular levels were unusually high for a secreted cystatin w 25 of the cystatin F in 2- or 4-day culture medium . By contrast U377 cehs nontaiced only 3-4 of the related inhibitor cysttaiin c. Cystatin F pur if led from lysates of U937 cells showed three major forms carrying two oee or no carbohydraee tt inas. mmnl ecyio-chemistry demonstrated a marked cytoplasmic cystatin F staining in a granular pattern. Double staining with a marker for endoplasmic reticulum revealed no colocalization for cystatin F. Analysis of the promoter region of the cystatin F gene CST7 showed that it iike that oI the iyaeCttm C gene CST3 ÍS deo old of typical TATA- and CAAT-hox ee--ments. In contrast to the cystatin C promoter it doss not contain multiple Sp1 binding sites but has a unique site for C EBPa Ịro ibnh explainmg the is ìrteiC d expressíon of thee cystatin F gene. Cells stimulated with cll-trans retinoic acid to differentiate them towards a granulocytic pathway showed a strong w 18-fold down-regulation of intraecllu-lar cystatin F and almost abolished secreted levels of the inhibitor. Stimulation with tetradecanoyl phorbol acetate causing monocytic differentiation also resulted in downregulation two fold to threefold of .
