RAPID ISOLATION OF ENDOSOMES FROM BHK CELLS - IDENTIFICATION OF DPP-IV (CD26) IN ENDOSOMES

In plasma membrane glycoproteins the peripheral monosaccharides of the N-glycan side chains are degraded faster than the core oligosaccharid es and the protein backbone. This intramolecular heterogenous turnover is a typical characteristic of membrane glycoproteins and is termed r emodeling or reprocessing. The mechanism of the reprocessing has been shown first for dipeptidyl peptidase TV (DPP TV, CD26). However, it is still a question in which subcellular compartment the enzyme machiner y for the reprocessing is located. Since lysosomes could be excluded, it has been proposed that the responsible glycosidases are located at the plasma membrane, in endosomes, or in the trans-Golgi network. The present study is concerned with the possible role of endosomes in this process of reprocessing. We transfected nonpolarized BHK cells with r at DPP IV cDNA. By establishing a fast and efficient method to purify endosomes, we could identify for the first time significant amounts of DPP IV in endosomes and we suggest therefore that endosomes are close ly related with the regulation of reprocessing of plasma membrane glyc oproteins. (C) 1996 Academic Press, Inc.