Binding requirements for latent transforming growth factor Beta2 activation.

Area of Science:

• Cell Biology
• Developmental Biology
• Biochemistry

Background:

• Latent transforming growth factor beta 1 (TGFβ1) and TGFβ3 activation mechanisms involve latency-associated peptide (LAP) binding to integrins and substrates.
• The activation mechanism for latent TGFβ2 has been unclear due to the absence of a classical integrin-binding sequence in its LAP.

Purpose of the Study:

• To investigate the requirement of covalent linkage for latent TGFβ2 activation.
• To determine if latent TGFβ2 activation depends on binding to matrix or cell surface proteins.

Main Methods:

• Generation of mutant mice with a TGFβ2 Cys residue (predicted to be involved in binding) mutated to Ser (Tgfb2).
• Phenotypic analysis of mutant mice, including survival, congenital defects, and TGFβ signaling.
• Measurement of secreted mutant latent TGFβ2 levels and TGFβ signaling via nuclear pSmad2.

Main Results:

• Mutant Tgfb2 mice exhibited phenotypes mirroring Tgfb2 null mice, including in utero lethality and congenital heart and kidney defects.
• Secreted mutant latent TGFβ2 levels were comparable to wild-type (WT).
• TGFβ signaling, monitored as nuclear pSmad2, was suppressed in mutant mice.

Conclusions:

• Latent TGFβ2 activation necessitates binding to an immobilized matrix or plasma membrane molecule.
• This finding clarifies the activation mechanism of latent TGFβ2, aligning it with TGFβ1 activation.
• Covalent linkage or specific binding interactions are crucial for latent TGFβ2 function during development.