Internalization of beta-adrenergic receptor binding sites: involvements of lysosomal enzymes
Chuang, D.M.
Biochemical and Biophysical Research Communications 105(4): 1466-1472
1982
ISSN/ISBN: 0006-291X PMID: 6285907 Document Number: 193365
Lysosomal enzymes were detected in a highly purified preparation of frog erythrocytes. Pretreatment of intact erythrocytes with lysosomotropic drugs reduced the number of soluble .beta.-receptors in isoproterenol-treated cells, whereas the level of membrane-bound receptors in these cells was unaffected. Subcellular fractionation by Percoll gradient centrifugation revealed that 1 species of lysosomes (density: 1.15 g/ml) contained a fraction of membrane-bound .beta.-adrenergic receptors. This fraction of membrane-bound receptors was markedly increased when desensitized cells were pretreated with chloroquine. The internalized receptors appear to be delivered to lysosomes and released from the endocytic vesicles by the lysosomal enzymes.