Related Experiment Videos
Mutational analysis of a transforming growth factor-beta receptor binding site
J K Burmester1, S W Qian, D Ohlsen
1Marshfield Medical Research Foundation, WI 54449, USA.
Abstract:
Transforming growth factor-beta s (TGF-beta 1, -beta 2, -beta 3) are important regulators of cell growth and differentiation which share approximately 70% identical amino acids. Using LS513 colorectal cells, which are growth inhibited by TGF-beta 1 (ED50 of 100 pM), but are refractory to TGF-beta 2 (ED50 of 50,000 to 100,000 pM), we have determined that amino acids 92-98 of TGF-beta specify growth inhibition. The chimeric protein TGF-beta 1/beta 2(92-98), in which amino acids 92-98 of TGF-beta 1 were exchanged for the corresponding amino acids of TGF-beta 2, was indistinguishable from TGF-beta 2 at inhibiting growth of LS513 cells. In contrast, both TGF-beta 1/beta 2(92-95) and TGF-beta 1/beta 2(94-98) inhibited the growth of LS513 cells with an ED50 of approximately 1000 pM. TGF-beta 1/beta 2(95-98), in which amino acids 95-98 of TGF-beta 1 have been replaced with the corresponding amino acids of TGF-beta 2, had full activity and was indistinguishable from TGF-beta 1. Receptor cross-linking experiments demonstrated that binding of the chimeras to the type I and type II receptors of LS513 cells was consistent with their biological activity. TGF-beta 1/beta 2(95-98), TGF-beta 1/beta 2(92-95) and TGF-beta 1/beta 2(94-98) were each similar to TGF-beta 2 in that they failed to bind to the soluble Type II receptor in a solid-phase assay. These results demonstrate that amino acids 92-98 are involved in the interaction between TGF-beta and its signaling receptors and they show that modest changes within this region can substantially alter biological response.
Insights
Transforming growth factor-beta (TGF-beta) amino acids 92-98 determine cell growth inhibition. Specific changes in this region alter TGF-beta
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- Transforming growth factor-beta (TGF-beta) isoforms (1, 2, 3) regulate cell growth and differentiation.
- LS513 colorectal cells exhibit differential sensitivity to TGF-beta isoforms, being inhibited by TGF-beta 1 but not TGF-beta 2.
Purpose of the Study:
- To identify the specific region of TGF-beta responsible for differential growth inhibition.
- To investigate the role of amino acids 92-98 in TGF-beta's interaction with its receptors.
Main Methods:
- Construction and testing of chimeric TGF-beta proteins with exchanged amino acid sequences.
- Assessing the biological activity of chimeric proteins in LS513 colorectal cells.
- Analyzing receptor binding affinities using receptor cross-linking and solid-phase assays.
Main Results:
- Amino acids 92-98 of TGF-beta 1 were identified as critical for growth inhibition in LS513 cells.
- A chimeric protein with TGF-beta 2 amino acids 92-98 (TGF-beta 1/beta 2(92-98)) lost growth inhibitory activity, similar to TGF-beta 2.
- Chimeras with partial exchanges (TGF-beta 1/beta 2(92-95), TGF-beta 1/beta 2(94-98)) showed reduced but significant activity.
- A chimera with TGF-beta 2 amino acids 95-98 (TGF-beta 1/beta 2(95-98)) retained full TGF-beta 1 activity.
- Receptor binding assays correlated with biological activity, indicating the importance of this region for receptor interaction.
Conclusions:
- The amino acid sequence 92-98 in TGF-beta plays a crucial role in specifying biological activity and receptor binding.
- Modifications within this specific region can significantly alter TGF-beta's effect on cell growth.
- These findings provide insights into the structure-function relationship of TGF-beta isoforms and their signaling pathways.