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Related Experiment Videos

Hsp70s and lysosomal proteolysis

S R Terlecky1

  • 1Department of Biology, University of California, San Diego, La Jolla 92093-0322.

Experientia
|November 30, 1994
PubMed
Summary
This summary is machine-generated.

Cells break down proteins using a lysosomal pathway when serum growth factors are withdrawn. A specific peptide sequence (KFERQ) targets proteins for degradation via the heat shock cognate protein of 73 kD (hsc73).

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Area of Science:

  • Cell Biology
  • Biochemistry
  • Molecular Biology

Background:

  • Cells utilize lysosomal pathways for protein degradation.
  • Serum growth factors influence cellular processes, including protein turnover.

Purpose of the Study:

  • To investigate the specific pathway of polypeptide breakdown in confluent cells upon serum withdrawal.
  • To identify the molecular determinants and proteins involved in selective protein degradation.

Main Methods:

  • Cell culture under serum-deprived conditions.
  • Analysis of cytosolic polypeptide substrates.
  • Biochemical assays to identify protein-binding sequences.
  • Investigating the role of heat shock cognate protein of 73 kD (hsc73) in lysosomal import.

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Main Results:

  • Confluent cells activate a lysosomal proteolytic pathway when serum growth factors are withdrawn.
  • A specific amino acid sequence (lysine-phenylalanine-glutamate-arginine-glutamine, KFERQ) is a key determinant for substrate recognition.
  • The heat shock cognate protein of 73 kD (hsc73) binds to KFERQ-related sequences and facilitates lysosomal degradation.
  • hsc73 is also found within lysosomes, suggesting a role in the proteolytic machinery.

Conclusions:

  • Selective lysosomal degradation of specific cytosolic polypeptides is mediated by the KFERQ motif.
  • hsc73 plays a dual role in recognizing and transporting substrates to the lysosome and potentially within the lysosome itself.
  • This pathway represents a critical mechanism for cellular protein quality control and adaptation to nutrient stress.