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Internalization of the fibronectin receptor is a constitutive process

M M Sczekan1, R L Juliano

  • 1Department of Pharmacology, University of North Carolina School of Medicine, Chapel Hill 27599-7365.

Journal of Cellular Physiology
|March 1, 1990
PubMed

Insights

Chinese Hamster Ovary (CHO) cell fibronectin receptors (FnR) are constitutively endocytosed, with about 30% internalized rapidly. The remaining FnR is shed upon antibody ligation, suggesting distinct receptor populations.

Area of Science:

  • Cell biology
  • Molecular and cell biology

Background:

  • The fibronectin receptor (FnR) plays a crucial role in cell adhesion and signaling.
  • Understanding the dynamic regulation of FnR on the cell surface is essential for comprehending cellular responses.

Purpose of the Study:

  • To investigate the endocytosis and shedding of the fibronectin receptor (FnR) in Chinese Hamster Ovary (CHO) cells.
  • To determine the proportion and kinetics of FnR internalization and identify potential distinct receptor populations.

Main Methods:

  • Quantification of internalized 125I-labeled anti-FnR antibody (PB1) after temperature shift.
  • Pharmacological disruption of vesicular traffic using monensin or chloroquine to assess FnR surface pool reduction.
  • Selective immunoprecipitation to differentiate surface and internalized 125I-labeled FnR.

Main Results:

  • Approximately 30% of cell surface FnR undergoes constitutive endocytosis with a half-time (t1/2) of 7 minutes.
  • Receptor internalization occurs independently of the receptor's ligation state.
  • 70-75% of cell surface FnR is shed upon antibody ligation at 37 degrees C, a slower process than internalization.

Conclusions:

  • CHO cells exhibit distinct populations of fibronectin receptors.
  • One population of FnR is constitutively endocytosed and potentially recycled.
  • Another larger fraction of FnR is shed from the cell surface upon ligation, suggesting it is unavailable for internalization.

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