title: Intracellular localization of the 74- and 53-kDa forms of L-histidine decarboxylase in a rat basophilic/mast cell line, RBL-2H3.
abstract: To clarify the process of post-translational modification of L-histidine decarboxylase (HDC), we investigated the conversion of the 74-kDa form of HDC into the 53-kDa form in specialized organella of a rat basophilic/mast cell line (RBL-2H3). With treatment of streptolysin-O, RBL-2H3 cells released approximately 40% of HDC activity accompanied by over 90% of lactate dehydrogenase activity. Only the 74-kDa form of HDC was detected in the leaked fraction by SDS-polyacrylamide gel electrophoresis. The 74-kDa form in the homogenate of pulse-labeled cells was recovered in both the supernatant and particulate fractions, while the 53-kDa form was detected only in the particulate fraction containing marker proteins of microsomes, Golgi, and lysosomal granules. Confocal microscopic observation using double staining immunofluorescence with anti-GST fusion HDC antiserum showed that most of the HDC coexists with protein-disulfide isomerase, a typical marker of the luminal space of the ER. With treatment of digitonin, RBL-2H3 cells released only 74-kDa HDC. Trypsin digestion of digitonin-permeabilized cells resulted in the disappearance of the 74-kDa form but not the 53-kDa form. From these results, it is assumed that the 74-kDa form of HDC, synthesized in the cytosol, is translocated into the lumen of the ER, where it is converted to the 53-kDa form.
authors.affiliation: Department of Physiological Chemistry, Faculty of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto 606, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Tanaka
authors.forename: K
authors.initials: K
authors.lastname: Nemoto
authors.forename: E
authors.initials: E
authors.lastname: Yamamura
authors.forename: A
authors.initials: A
authors.lastname: Ichikawa
mesh_terms: D000818:Animals; D001491:Basophils / Q000201:enzymology*; D002460:Cell Line; D006640:Histidine Decarboxylase / Q000378:metabolism*; D018613:Microscopy, Confocal; D011499:Protein Processing, Post-Translational; D051381:Rats
chemical_list: D006640:Histidine Decarboxylase