Protein degradation in skin fibroblasts from patients with Duchenne muscular dystrophy

Abstract

The rates of degradation of [3H]leucine-labelled proteins have been measured in cultures of skin fibroblasts obtained from normal controls (five subjects) and patients with Duchenne muscular dystrophy (six subjects). Cultures were incubated with [3H]leucine (10 microCi/ml) for 60 min to label "short-lived" proteins, and with [3H]leucine (5 microCi/ml) for 60 h to label "long-lived" proteins. Optimal wash procedures were devised for removal of [3H]leucine from the extracellular space and from cell pools before beginning degradation measurements. Re-utilization of [3H]leucine released from degraded labelled proteins was prevented by supplementing the medium with 4mM-leucine. Rates of degradation did not depend on the growth state of the cells or on cell age over the range used (passages eight-20). Degradation of long-lived proteins was approximately linear over a 24h period, at a rate of 1.0% per h. 30% of short-lived protein was degraded within 6h. No differences were observed between protein degradation in normal fibroblasts and in those from patients with Duchenne muscular dystrophy.

Historical aspects of muscle research in the Dubowitz Neuromuscular Centre: the Hammersmith days

“…Differences in adhesion and cell movement between cells from normal and dystrophic patients were found, supporting the hypothesis of a cell membrane defect in Duchenne muscular dystrophy [6 , 7] . With Helen Statham, protein degradation and calcium handling were also studied [8] . The involvement and importance of calcium in diseased muscle was already appreciated at that time and Rena Yarom from Jerusalem, who did a sixmonth sabbatical with us, persuaded me to look at calcium in dystrophic muscle and in Duchenne muscular dystrophy (DMD) carriers with electron microscopic X-ray analysis, studies which formed the basis of my PhD [9 , 10] .…”

Differential degradation of [35S]methionine polypeptides in Duchenne muscular dystrophy skin fibroblasts in vitro.

“…DMD skin fibroblast populations in vitro express a variety of syndrome-specific cellbiological (6)(7)(8)(9)(10), and biochemical (11)(12)(13)(14)(15)(16)(17) abnormalities. Recent investigations into the protein turnover in DMD fibroblasts in vitro (18)(19)(20) (17) and from our laboratory (20) indicate a significant decrease in protein synthesis (17,20) and a significant increase in the degradation of short-and long-lived proteins in DMD fibroblast populations in vitro (20).…”