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Proteolysis in human lens epithelium determined by a cell-permeable substrate

Artikel i vetenskaplig tidskrift
Författare Jan-Olof Karlsson
Madeleine Andersson
Anne Kling-Petersen
Johan Sjöstrand
Publicerad i Invest Ophthalmol Vis Sci
Volym 40
Nummer/häfte 1
Sidor 261-4
Publiceringsår 1999
Publicerad vid Institutionen för klinisk neurovetenskap, Sektionen för oftalmologi
Institutionen för anatomi och cellbiologi
Sidor 261-4
Språk en
Länkar www.iovs.org/cgi/content/abstract/4...
Ämnesord Acetylcysteine/analogs &amp, derivatives/pharmacology, Calcium/metabolism, Calpain/*metabolism, *Cell Membrane Permeability, Cell Survival, Coumarins/*metabolism, Cysteine Endopeptidases/*metabolism, Enzyme Inhibitors/pharmacology, Epithelium/drug effects/enzymology, Human, Ionomycin/pharmacology, Lactate Dehydrogenase/metabolism, Lens, Crystalline/drug effects/*enzymology, Multienzyme Complexes/*metabolism, Oligopeptides/*metabolism, Substrate Specificity, Support, Non-U.S. Gov't, Thapsigargin/pharmacology
Ämneskategorier Cell- och molekylärbiologi

Sammanfattning

PURPOSE: To develop a system for continuous evaluation of proteolytic activity in human lens epithelium and to characterize factors of importance for the regulation of proteolytic activity in lens epithelial cells. METHODS: Human lens epithelial cells were obtained during cataract surgery. Capsule epithelium specimens consisted of the central parts of the anterior capsule and the underlying lens epithelium. The sample, with the cell-permeable substrate Suc-Leu-Leu-Val-Tyr-7-amino-4-methylcoumarin, was placed in a chamber, which was placed in a thermostat-controlled aluminum block. Fluorescence changes were continuously measured by the fiber optics of the luminometer, which was placed 5 mm above the buffer surface. RESULTS: After administration of substrate to the medium overlying the cells, the substrate was degraded at a relatively slow rate. Approximately 10 picomoles of amino-4-methylcoumarin were formed per minute. A significant increase of proteolytic activity could be observed after application of 1 microM ionomycin or 2 microM thapsigargin. No leakage of lactate dehydrogenase from the cells was observed during these procedures. Basal proteolytic activity was totally inhibited by the proteasome inhibitor lactacystin. Lactacystin also attenuated the response to ionomycin and thapsigargin. CONCLUSIONS: Human lens epithelium responds to increased Ca levels from external or internal stores with an increased proteolytic activity that may be mediated by calpain, by the proteasome, or by both. This calcium-dependent change in proteolytic activity may be of importance in the development of cataract.

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