Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.1 (chymotrypsin)
 10,938 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The 70-kDa neurofilament protein subunit (NF-L) is phosphorylated in vivo on at least three sites (L1 to L3) (Sihag, R. K. and Nixon, R. A. (1989) J. Biol. Chem. 264, 457-464). The turnover of phosphate groups on NF-L during axonal transport was determined after the neurofilaments in retinal ganglion cells were phosphorylated in vivo by injecting mice intravitreally with [32P]orthophosphate. Two-dimensional phosphopeptide maps of NF-L from optic axons of mice 10 to 90 h after injection showed that radiolabel decreased faster from peptides L2 and L3 than from L1 as neurofilaments were transported. To identify phosphorylation sites on peptide L2, axonal cytoskeletons were phosphorylated by protein kinase A in the presence of heparin. After the isolated NF-L subunits were digested with alpha-chymotrypsin, 32P-peptides were separated by high performance liquid chromatography on a reverse-phase C8 column. Two-dimensional peptide mapping showed that the alpha-chymotrypsin 32P-peptide accepting most of the phosphates from protein kinase A migrated identically with the in vivo-labeled phosphopeptide L2. The sequence of this peptide (S-V-R-R-S-Y) analyzed by automated Edman degradation corresponded to amino acid residues 51-56 of the NF-L sequence. A synthetic 13-mer (S-L-S-V-R-R-S-Y-S-S-S-S-G) corresponding to amino acid residues 49-61 of NF-L was also phosphorylated by protein kinase A. alpha-Chymotryptic digestion of the 13-mer generated a peptide which contained most of the phosphates and co-migrated with the phosphopeptide L2 on two-dimensional phosphopeptide maps. Edman degradation of the phosphorylated 13-mer identified serine residue 55 which is located within a consensus phosphorylation sequence for protein kinase A as the major site of phosphorylation. Since protein kinase A-mediated phosphorylation influences intermediate filament assembly/disassembly in vitro, we propose that the phosphopeptide L2 region is a neurofilament-assembly domain and that the cycle of phosphorylation and dephosphorylation of Ser-55 on NF-L, which occurs relatively early after subunit synthesis in vivo, regulaaes a step in neurofilament assembly or initial interactions during axonal transport.
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PMID:Identification of Ser-55 as a major protein kinase A phosphorylation site on the 70-kDa subunit of neurofilaments. Early turnover during axonal transport. 171 55

Ten polyclonal neurofilament antibodies were tested for domain specificity with immunoblots of chymotrypsin digests of a neurofilament protein of 150 kDa (NF 150K). In contrast to most monoclonal antibodies previously reported, the five polyclonal antibodies which showed domain specificity reacted with the 40 kDa alpha-helical rod domain of the molecule. (With one exception, monoclonal antibodies reacted with the 100 kDa carboxy-terminal peripheral domain). Of these ten polyclonal antibodies only two reacted with an isoelectric variant of NK 150K (S150) isolated by Liem and collaborators (Wong, J., Hutchison, S.B. and Liem, R.K.H. (1984) J. Biol. Chem. 259, 10867-10874) from bovine brain. 13 monoclonal antibodies were also tested for reactivity with S150 protein. With one exception, none of these antibodies reacted with this variant, not even a monoclonal antibody which we have previously shown to react with a non-phosphorylated epitope located in the rod domain of NF 150K. We suggest that either there are modifications other than dephosphorylation in the S150 isoelectric variant or, alternatively, that it is not derived from NF 150K.
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PMID:Immunological study of a neurofilament protein variant (S150) with polyclonal and monoclonal antibodies. 244 63

Gliosarcomas contain both neuro-ectodermal and mesenchymal elements. Its histogenesis has been much debated and endothelial and adventitial fibroblast origins have been suggested, as has a "histiocytic" origin following the demonstration of antiprotease activity. Eight gliosarcomas have been examined with a panel of ten monoclonal and polyclonal antibodies to investigate the origin of the sarcomatous element. Glial fibrillary acid protein expression showed a sharp distinction between gliomatous and sarcomatous tumour components. Contrary to some previous reports factor 8-related antigen and Ulex europeus agglutinin stained vascular luminal endothelium but no tumour cells. Vimentin and fibronectin expression was extensive and confined largely to sarcomatous areas. Desmin and neurofilament protein could not be demonstrated in any of the cases. Numerous cells, particularly in the sarcoma areas, expressed alpha-1-antitrypsin and -chymotrypsin. A proportion of these stained for the monocyte/macrophage marker MAC 387. Four cases focally exhibited a true storiform pattern and this and the immunohistochemical results suggest analogies with the fibrous histiocytomas. These tumours contain reactive histiocytes but are now thought to be derived from fibroblasts or from pluripotent mesenchymal cells in perivascular adventitia. This resembles the pattern exhibited in the sarcomatous component of gliosarcomas.
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PMID:Gliosarcoma: an immunohistochemical study. 260 37