Key result
Rat neonatal cardiomyocytes express high-affinity TGF-beta 2 receptors with ~5,000 binding sites per cell.
Why the study?
The molecular characteristics and binding properties of a high-affinity TGF-beta 2 receptor on cardiomyocytes were not fully defined.
Rat neonatal cardiomyocytes express a high-affinity, selective surface receptor for TGF-beta 2, suggesting a receptor-mediated mechanism for its anti-ischemic cardioprotective effects.
Supports receptor-mediated TGF-β2 signaling in rat cardiomyocytes; leaves open translation to human cardioprotection.
Rat neonatal heart muscle cells (cardiomyocytes) were found to express a high-affinity surface receptor for transforming growth factor-beta 2 (TGF-beta 2). Specific binding was rapid, saturable, ligand-selective, and reversible. Equilibrium binding analyses revealed that the cardiomyocyte had one class of specific binding sites with a Kd < or = 26 pM TGF-beta 2, a Bmax of approximately 9 fmol/10(6) cells, and approximately 5,000 binding sites/cardiomyocyte. Binding was selective for TGF-beta 2 in comparison to other TGF-beta isoforms and to unrelated growth factors. Affinity-binding experiments revealed three types of cardiomyocyte TGF-beta 2 binding proteins, the most prominent of which corresponded to the high-molecular mass proteoglycan. These data raise the possibility that the anti-ischemic cardioprotective effects of TGF-beta may reflect receptor-mediated signal transduction at the cardiomyocyte level.
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Ross et al. (1993) studied this question. TGF-beta 2 vs. Other TGF-beta isoforms and unrelated growth factors was evaluated on Receptor binding characteristics (Kd, Bmax, binding sites). Rat neonatal cardiomyocytes express a high-affinity surface receptor for TGF-beta 2 with a Kd ≤ 26 pM and approximately 5,000 binding sites per cell.
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