Kinetics of intracellular degradation of newly synthesized collagen

Biochemistry. 1986 May 6;25(9):2455-9. doi: 10.1021/bi00357a024.

Abstract

The objective of this work was to determine the time dependence of the basal component of intracellular degradation of newly synthesized collagen. Chick embryo tendon fibroblasts were incubated with [14C]proline, and degradation was quantified by measuring hydroxy[14C]proline in a low molecular weight fraction. When cultures were pulse labeled for 15 min and then incubated under chase conditions for 105 min, the amount of degraded collagen attained a value equal to approximately 20% of the amount synthesized during the labeling period; the data were fit with a simple exponential function that had a 40-min rise time and a 12-min lag time. In continuously labeled cultures, the rates of collagen synthesis and secretion reached constant values within 15 and 45 min, respectively. Degradation products were first detected 6-9 min after collagen synthesis began and were transported out of the cells more rapidly than intact collagenous molecules; however, percent degradation increased slowly and did not reach a constant value even after 240 min of incubation. Since collagen degradation lags collagen synthesis, it follows that degradation is a posttranslational, rather than a cotranslational, process, and since degradation and secretion are kinetically distinguishable, it follows that they occur in parallel pathways. A simple nonlinear model for posttranslational processing of collagen is proposed.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Carbon Radioisotopes
  • Cells, Cultured
  • Chick Embryo
  • Collagen / biosynthesis
  • Collagen / metabolism*
  • Fibroblasts / metabolism
  • Kinetics
  • Proline / metabolism
  • Radioisotope Dilution Technique
  • Tendons / metabolism*
  • Tritium

Substances

  • Carbon Radioisotopes
  • Tritium
  • Collagen
  • Proline