Effects of cysteine protease inhibitors on rabbit cathepsin D maturation

Journal Article · Thu Nov 30 23:00:00 EST 1989 · American Journal of Physiology; (USA)

OSTI ID:7195065

Samarel, A M; Ferguson, A G; Decker, R S; Lesch, M ^[1]

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1. Loyola Univ., Stritch School of Medicine, Maywood (USA)

To examine the effects of cysteine protease inhibitors on cathepsin D intracellular transport, proteolytic processing, and secretion, primary cultures of rabbit cardiac fibroblasts were grown to confluence and exposed to media containing leupeptin, E 64, or chloroquine. Cathepsin D maturation was then evaluated in pulse-chase biosynthetic labeling experiments. None of the three agents affected the charge modification of procathepsin D within the Golgi apparatus. However, all three agents interfered with the subsequent proteolytic processing of procathepsin D isoforms to active cathepsin D. Both leupeptin and E 64 caused the intracellular accumulation of large amounts of a Mr 51,000 processing intermediate. Trace amounts of this intermediate were also detected in chloroquine-treated cells. Combined activity assay and radioimmunoassay of cell lysates indicated that this partially processed form of cathepsin D possessed proteolytic activity. Whereas low medium concentrations of leupeptin (10-100 microM) but not E 64 appeared to stimulate procathepsin D secretion, neither agent appeared to have a major effect on the rate of proenzyme secretion at doses required to inhibit proteolytic maturation (1-10 mM). Furthermore, pretreatment of cells with 10 mM leupeptin appeared only to delay, but not prevent, the intracellular transport of cathepsin D to lysosomes. In contrast, chloroquine increased procathepsin D secretion in a dose-dependent manner, diverting the majority of newly synthesized procathepsin D from the intracellular protease(s) responsible for proteolytic processing. These results suggest that cysteine proteases participate in the proteolytic maturation of procathepsin D during the transport of newly synthesized enzyme to lysosomes, but cysteine protease-mediated proteolytic processing is not required for cathepsin D activation or lysosomal translocation.

• OSTI ID: 7195065
• Journal Information: American Journal of Physiology; (USA), Journal Name: American Journal of Physiology; (USA) Vol. 257; ISSN 0002-9513; ISSN AJPHA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
AMINO ACIDS
ANIMAL CELLS
ANIMALS
BIOASSAY
BIOCHEMICAL REACTION KINETICS
BODY
CARBOXYLIC ACIDS
CARDIOVASCULAR SYSTEM
CATHEPSINS
CELL CONSTITUENTS
CELL CULTURES
CHEMICAL REACTIONS
CONNECTIVE TISSUE CELLS
CYSTEINE
DECOMPOSITION
DIAGNOSTIC TECHNIQUES
DOSE-RESPONSE RELATIONSHIPS
DRUGS
ENZYME ACTIVITY
ENZYME INHIBITORS
ENZYMES
FIBROBLASTS
HEART
HYDROLASES
IMMUNOASSAY
IMMUNOLOGY
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LEUCINE
LIPOTROPIC FACTORS
LYSOSOMES
MAMMALS
MEMBRANE TRANSPORT
METHIONINE
MUSCLES
MYOCARDIUM
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
ORGANOIDS
ORGANS
PEPTIDE HYDROLASES
PROTEOLYSIS
RABBITS
RADIOASSAY
RADIOIMMUNOASSAY
RADIOIMMUNODETECTION
RADIOIMMUNOLOGY
REACTION KINETICS
SECRETION
SH-PROTEINASES
SOMATIC CELLS
SULFUR ISOTOPES
THIOLS
TRACER TECHNIQUES
VERTEBRATES