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Alpha-fetoprotein binding and uptake by primary cultures of human skeletal muscle
H C Lorenzo1, M Geuskens, A Macho
1Laboratoire de Chimie des Protéines, Institut de Recherches sur le Cancer, Villejuif, France.
Insights
Human myoblasts internalize alpha-fetoprotein (AFP) during development, likely for fatty acid delivery. This binding ability decreases significantly in more mature muscle cells (myotubes).
Area of Science:
- Cell Biology
- Developmental Biology
- Biochemistry
Background:
- Alpha-fetoprotein (AFP) is a serum protein synthesized by the fetal liver and yolk sac.
- AFP acts as a major carrier of polyunsaturated fatty acids during embryonic development.
- Fetal cells undergoing growth and differentiation exhibit AFP binding and internalization.
Purpose of the Study:
- To investigate the binding and endocytosis of alpha-fetoprotein (AFP) by human muscle cells in vitro.
- To examine AFP interaction with human myoblasts and myotubes at different differentiation stages.
Main Methods:
- Primary cultures of human skeletal muscle cells (myoblasts and myotubes) were used.
- Cells were incubated with colloidal-gold-conjugated human AFP.
- Techniques included light microscopy, electron microscopy, and laser scanning confocal microscopy.
Main Results:
- Human myoblasts demonstrated binding and internalization of AFP, suggesting specific receptor involvement.
- This AFP uptake capability was significantly reduced or absent in differentiated myotubes.
- AFP was also observed binding to the extracellular matrix of both myoblasts and myotubes.
Conclusions:
- Human myoblasts actively bind and internalize AFP during growth and differentiation.
- The physiological role of AFP uptake may involve delivering essential fatty acids to developing fetal cells.
- The interaction of AFP with muscle cells changes significantly with cellular differentiation.
Abstract:
alpha-Fetoprotein (AFP), a serum alpha-globulin mainly synthesized by the fetal liver and the yolk sac, is the major carrier of polyunsaturated fatty acids during embryo-fetal development. One property characteristic of fetal cells undergoing growth and differentiation is their ability to bind and internalize AFP. In the present work, we have studied the binding and endocytosis of AFP by human muscular cells developing in vitro. Primary cultures of human skeletal muscle, obtained from biopsies and examined at two stages of differentiation (myoblasts and myotubes), were incubated for different times, at 0 and 37 degrees C, with a colloidal-gold-conjugated human AFP probe and studied by light and electron microscopy, as well as by laser scanning confocal microscopy in the reflection mode. The results obtained show that (a) human myoblasts in primary culture bind and internalize the protein, probably through specific AFP receptors, (b) this property is strongly reduced or lost in well-differentiated myotubes, and (c) AFP is also bound, throughout culture development, to the extracellular matrix of fusing myoblasts and differentiated myotubes. The physiological significance of AFP uptake by human myoblasts undergoing growth and differentiation may be based on the ability of AFP to carry and deliver fatty acids to fetal cells.
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