Cell type-dependent variations in the subcellular distribution of alpha-mannosidase I and II.

alpha-mannosidases I and II (Man I and II) are resident enzymes of the Golgi complex involved in oligosaccharide processing during N-linked glycoprotein biosynthesis that are widely considered to be markers of the cis- and medial-Golgi compartments, respectively. We have investigated the distribution of these enzymes in several cell types by immunofluorescence and immunoelectron microscopy. Man II was most commonly found in medial- and/or trans- cisternae but showed cell type-dependent variations in intra-Golgi distribution.

Biosynthetic and structural studies on Thy-1 in a rat neuronal tumor cell line.

Because of the limited information available about the synthesis of N-linked glycoproteins in nerve cells, in regard to both processing steps and enzyme characterization, the biosynthetic processing of Thy-1 of the rat neuronal tumor cell line BN-1010-1 has been investigated using several inhibitors of biosynthesis and transport. (i) Tunicamycin completely inhibited mannose incorporation into Thy-1. Unglycosylated Thy-1 was not transported to the cell surface and was probably degraded rapidly following synthesis.

Formation, turnover, and sensitivity to phosphatidylinositol-specific phospholipase C of Thy-1 of a rat neuronal tumor cell line.

We have investigated the formation, turnover, and sensitivity to phosphatidylinositol-specific phospholipase C (PI-PLC) of Thy-1 in the rat neuronal tumor cell line BN-1010-1. It was initially established that a relatively short labeling time (1.5 h) using [3H]mannose yielded much more highly labeled PI-PLC-releasable glycoproteins than a longer labeling time (18 h).

Evidence that swainsonine pretreatment of rats leads to the formation of autophagic vacuoles and endosomes with decreased capacity to mature to, or fuse with, active lysosomes.

The plant toxin swainsonine causes a variety of biochemical and morphological changes in animal tissues. In rat liver there is an extensive vacuolization which is not accompanied by an accumulation of oligosaccharide. In investigating this proliferation of autophagic vacuoles we have found that swainsonine administration leads to a shift in the density of liver lysosomes as indicated by the distribution of several lysosomal glycosidases in sucrose gradients.

Novel purification of the catalytic domain of Golgi alpha-mannosidase II. Characterization and comparison with the intact enzyme.

Rat liver alpha-mannosidase II, a hydrolase involved in the processing of asparagine-linked oligosaccharides, is an integral membrane glycoprotein facing the lumen of Golgi membranes. We have previously shown (Moremen, K. W.