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- Title
Low Temperature Blocks Transport and Sorting of Cathepsin D in Fibroblasts.
- Authors
BRAULKE, Thomas; HASILIK, Andrej; von FIGURA, Kurt
- Abstract
The transport of newly synthesized cathepsin D in fibroblasts at 16-28 °C was compared to that at 37 °C. At 37 °C newly synthesized cathepsin D passes the trans Golgi within 30-60 min, becomes segregated from the secretory route into prelysosomal organelles within 1-2 h and processed to mature forms in dense lysosomes within 1.5-3 h after synthesis. The small fraction of cathepsin D that escapes transport into lysosomes is secreted within less than 2 h. At 16-28 °C the transport of cathepsin D to lysosomes is inhibited in a temperature-dependent manner. At 16-28 °C cathepsin D precursors are slowly transported to the trans Golgi. The cathepsin D precursors accumulate at a site that is in continuity with the secretory pathway and located within or distal of the trans Golgi and proximal to the site where cathepsin D precursors leave the secretory pathway as complexes with mannose 6-phosphate receptors. The arrest at this site is not complete. The receptor- dependent segregation of the cathepsin D precursors released from the block is impaired at ≤ 26 °C. The inhibition of segregation results in an increased, albeit retarded secretion of cathepsin D. The fraction of cathepsin D precursors that is segregated from the secretory pathway encounters a further low temperature block in prelysosomal organelles. There cathepsin D precursors are proteolytically processed to an intermediate form, which accumulates transiently. The present results indicate that low temperature impairs the transport of newly synthesized lysosomal enzymes along all sections of the lysosomal pathway and interferes with the segregation of lysosomal enzyme precursors from the secretory route.
- Publication
Biological Chemistry, 1988, Vol 369, Issue 1, p441
- ISSN
1431-6730
- Publication type
Article