The deleted in brachydactyly B domain of ROR2 is required for receptor activation by recruitment of Src

Area of Science:

• Molecular Biology
• Cell Signaling
• Genetics

Background:

• ROR2 is a transmembrane receptor tyrosine kinase implicated in skeletal development.
• Mutations in ROR2 cause Robinow Syndrome (RS) and Brachydactyly type B (BDB), highlighting its critical role.
• The precise signal transduction mechanisms of ROR2 have remained largely unknown.

Purpose of the Study:

• To elucidate the signal transduction mechanisms of the ROR2 receptor.
• To investigate the role of the ROR2 C-terminal domain in receptor activity.
• To understand the molecular basis of Brachydactyly type B (BDB) associated with ROR2 mutations.

Main Methods:

• Utilized a constitutive dimerization approach to study ROR2 activity.
• Employed mass spectrometry to identify phosphorylation sites.
• Investigated the effect of Wnt5a ligand and Src kinase inhibition on ROR2 phosphorylation.
• Analyzed receptor internalisation using Rab5 positive endosomes.

Main Results:

• ROR2 exhibits dimerization-induced tyrosine kinase activity.
• The ROR2 C-terminal domain is essential for recruiting and activating the non-receptor tyrosine kinase Src.
• Wnt5a ligand induces native ROR2 phosphorylation, which is dependent on Src kinase activity.
• Identified eight Src-mediated ROR2 phosphorylation sites.
• Activated ROR2 undergoes internalisation into Rab5 positive endosomes.
• BDB mutant receptors show defective kinase activation due to impaired Src recruitment.

Conclusions:

• ROR2 activation is mediated by Src kinase, with the C-terminal domain being crucial for this interaction.
• Brachydactyly type B (BDB) arises from a failure in ROR2 kinase activation due to the inability to recruit Src.
• These findings provide critical insights into ROR2 signaling and its role in skeletal dysmorphology.