The key difference between TGF alpha and beta is that TGF alpha is an epidermal growth factor that induces epithelial development while TGF beta is a cytokine-based growth factor that participates in numerous signalling pathways in a cell.
TGF alpha and beta are two classes of polypeptide growth factors which take part in many functions of the cell. Both these growth factors act via a signalling cascade to alter cellular functions. Although they show similar responses, they differ in their genetics and the structure. In fact, two different genes code for these two growth factors. Amino acid sequence and the length of the sequences are also different among these two proteins.
CONTENTS
1. Overview and Key Difference
2. What is TGF Alpha
3. What is TGF Beta
4. Similarities Between TGF Alpha and Beta
5. Side by Side Comparison – TGF Alpha vs Beta in Tabular Form
6. Summary
What is TGF Alpha?
Transforming growth factor (TGF) alpha is a protein that acts as an epidermal growth factor. TGFA gene codes for the TGF alpha protein. It is a mitogenic polypeptide chain. Phosphorylation activates the inactive form of TGF alpha protein into the active form. The precursor TGF alpha molecule is a transmembrane precursor which contains 160 amino acids. Also, it consists of a hydrophobic part (transmembrane domain) and a hydrophilic cytosolic domain. Its synthesis primarily takes place in the gastric mucosa. Cells such as macrophages, brain cells and keratinocytes carry out the production of TGF alpha.
Figure 01: TGF Alpha
TGF alpha acts as a ligand for the epidermal growth factor receptor (EGFR) and initiates signalling cascades for processes such as cell proliferation, cell differentiation and cell development. The TGF alpha also associates with many types of cancers and promotes angiogenesis in cancer cells. Thus, in cancer cells, there is overexpression of TGF alpha in comparison to normal healthy cells.
What is TGF Beta?
TGF beta is a cytokine. There are three isoforms of TGF beta as TGF Beta 1, 2 and 3. They are large proteins ranging from about 380 amino acids to 412 amino acids. Moreover, the genes TGFB1, TGFB2 and TGFB3 code for the respective isoforms of TGF beta cytokines. The production of TGF beta isoforms takes place in all types of white blood cell lineages.
Figure 02: TGF Beta
The TGF beta cytokines bind to the type 2 receptor kinases. Then they undergo phosphorylation. Upon phosphorylation, they gain the ability to phosphorylate type 1 receptor kinases. Via the signalling cascade, TGF beta cytokines participate in a variety of functions including cell regulatory activities, induction of transcription, chemotaxis and the activation of many immune cells.
What are the Similarities Between TGF Alpha and Beta?
- TGF Alpha and Beta are two classes of polypeptide growth factors.
- They are made up of amino acids.
- Binding to respective receptors is necessary to activate both proteins.
- They undergo phosphorylation reactions upon binding to their respective receptors to activate signalling cascades.
- Both alter the genetic expression of proteins and regulate cellular activities.
- Moreover, both function in the immune responses of cells.
- Also, they play a major role in cancer biology.
What is the Difference Between TGF Alpha and Beta?
TGF alpha and beta are two polypeptide growth factors. TGF alpha is an epidermal growth factor that induces epithelial development while TGF beta is a cytokine-based growth factor that participates in numerous signalling pathways of cellular regulation and immune responses. So, this is the key difference between TGF alpha and beta.
Moreover, although both are proteins, they differ in the length of the amino acid sequence. The TGF alpha protein has a sequence of 160 amino acids, while TGF beta isoforms have sequences ranging from 380 to 421 amino acids. Therefore, we can consider this also as a difference between TGF alpha and beta.
The below infographic summarizes the difference between TGF alpha and beta, comprehensively.
Summary – TGF Alpha vs Beta
TGF alpha and beta play a major role in signal transduction to alter the cellular activities in response to various immune responses. In summary, the key difference between TGF alpha and beta is that the TGF alpha acts like an epithelial growth factor, whereas TGF beta acts as a cytokine. They are encoded by different genes; hence, they do not show the genetic relationship. Also, the binding of both TGF alpha and beta to their receptors is necessary to activate them and participate in a signalling cascade in the cell. Furthermore, both TGF alpha and beta play an important role in generating immune responses. Thus, this summarizes the difference between TGF alpha and beta.
Reference:
1. Salajegheh, Ali. “Transforming Growth Factor α and β (TGF-α and TGF-β).” SpringerLink, Springer, Cham, 1 Jan. 1970, Available here.
Image Courtesy:
1. “Protein TGFA PDB 1mox” By Emw – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “TGF beta pathway 2” By Jerome Walker – Own work (CC BY 2.5) via Commons Wikimedia