Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.5.1.52 (PNGase F)
 1,527 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We describe the isolation of human fibronectin receptors (integrins) from two nonadherent promonocytic cell lines and from peripheral blood monocytes. Integrins purified from U-937 and THP-1 cells exhibited identical electrophoretic migrations on sodium dodecyl sulfate gels run under reducing (approximately Mr 150,000) and nonreducing (alpha, Mr 160,000; beta, Mr 130,000) conditions. Treatment of U-937 or THP-1 cells with phorbol esters induced these cells to express different integrins with electrophoretic mobilities (alpha, Mr 140,000; beta, Mr 115,000, nonreduced) identical to those from normal human peripheral blood monocytes. Receptors isolated from uninduced, nonadherent promonocytic leukemia cells (U-937 and THP-1) were distinct from glycoproteins IIb and IIIa and from leukocyte adhesion molecules (p150/95). However, receptors isolated here did react with an antibody known to block cell adhesion to fibronectin. The differences observed in apparent molecular masses of fibronectin receptors from uninduced and induced U-937 or THP-1 cells are removed by treatment of purified integrins with endoglycosidase F or N-glycanase. In summary, the data presented here demonstrate the purification of integrins by fibronectin affinity chromatography from human leukemia cells and normal peripheral blood monocytes. Our results suggest that these receptors differ in immature and mature monocytic cells, and are altered by glycosylation in the course of cellular maturation.
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PMID:Alteration of fibronectin receptors (integrins) in phorbol ester-treated human promonocytic leukemia cells. 297 31

The p150,95 cell surface protein is a member of a family of heterodimeric leukocyte adhesion proteins that have homologous alpha subunits, each noncovalently associated with a common beta subunit. In this report we have metabolically labeled the U937 cell line at various timepoints during its phorbol myristic acetate-induced maturation to examine the kinetics of synthesis of these proteins during monocytic differentiation, and their maturation and glycosylation. The p150,95 alpha subunit was immunoprecipitated with p150,95-specific monoclonal antibody (MAb), or an antiserum to the denatured, purified alpha X subunit. The glycosylation and polypeptide chain length of the p150,95, Mac-1, and lymphocyte function associated antigen (LFA-1) alpha and beta subunits were compared by immunoprecipitation with subunit specific MAb and antisera, and by digestion with Endo H and N-glycanase. The p150,95 alpha subunit is synthesized as a precursor of 146,000 Mr, has five to six N-linked oligosaccharides, and has a polypeptide chain backbone of 132,000 Mr. Over 50% of the carbohydrate on the mature alpha subunit of 150,000 Mr was sensitive to Endo H digestion. The p150,95 alpha and beta precursors can associate before maturation into the mature form. Conversion to the mature form was accompanied by loss of reactivity with the antiserum to the denatured alpha X subunit, suggesting a change in conformation. Mac-1 and LFA-1 alpha subunits have precursors of 160,000 Mr and 165,000 Mr, respectively, and contain N-linked carbohydrates. The polypeptide chain length for the Mac-1 alpha subunit is 137,000 Mr, and for LFA-1 is 149,000 Mr. Only 14% of the oligosaccharide on the mature LFA-1 alpha subunit was sensitive to Endo H, suggesting that unlike p150,95, most is converted to the complex type. The differences noted in the Mr of the three homologous alpha subunits are therefore due to differences in both polypeptide chain length and carbohydrate processing during biosynthesis.
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PMID:Biosynthesis and glycosylation of p150,95 and related leukocyte adhesion proteins. 329 34