FGFR3 unliganded dimer stabilization by the juxtamembrane domain.

Area of Science:

• Molecular Cell Biology
• Biochemistry
• Structural Biology

Background:

• Receptor tyrosine kinases (RTKs) mediate cellular signals through dimerization.
• Unliganded RTK dimers are critical signaling intermediates, distinct from ligand-induced activation.
• Fibroblast growth factor receptor 3 (FGFR3) is vital for skeletal development.

Purpose of the Study:

• To investigate the role of the juxtamembrane (JM) domain in the unliganded dimer stability of FGFR3.
• To understand the contribution of the JM domain relative to other FGFR3 domains and mutations.

Main Methods:

• Direct investigation of the JM domain's effect on unliganded FGFR3 dimer stability.
• Analysis of receptor-receptor contacts involving JM domains.
• Assessment of additive effects between JM domain and transmembrane (TM) domain mutations.

Main Results:

• FGFR3 unliganded dimers are stabilized by receptor contacts involving the JM domains.
• JM domain contribution to stabilization is comparable to pathogenic mutations and extracellular (EC) domain repulsion.
• JM and TM pathogenic mutations exhibit additive effects on unliganded dimer stability.
• JM-mediated stabilization requires linkage to the TM domain, not just membrane anchoring.

Conclusions:

• The JM domain plays a significant role in stabilizing unliganded FGFR3 dimers.
• Coordinated action of JM and TM domains stabilizes the unliganded dimeric state of FGFR3.
• This stabilization mechanism differs from that observed in other RTKs like EGFR.