Interplay of Specific Trans- and Juxtamembrane Interfaces in Plexin A3 Dimerization and Signal Transduction

Area of Science:

• Molecular Biology
• Cell Signaling
• Developmental Biology

Background:

• Plexins are transmembrane receptors involved in cellular guidance and development.
• Receptor dimerization, influenced by transmembrane (TM) and juxtamembrane (JM) domains, is critical for plexin activity.
• The precise roles of TM and JM domains in plexin signal transduction are not fully understood.

Purpose of the Study:

• To investigate the interplay between plexin TM and JM domains in regulating plexin A3 homodimerization and signaling.
• To elucidate the structural interfaces governing plexin A3 dimerization.

Main Methods:

• Integrated experimental (mutagenesis) and simulation (molecular dynamics) approaches.
• Utilized Danio rerio Plexin A3.
• Assessed signaling through a zebrafish axonal guidance assay.

Main Results:

• Disruption of TM domain small-x3-small motifs enhanced JM-mediated dimerization.
• Mutations in the JM heptad repeat disrupted dimerization independently of TM domain mutations.
• TM interface mutations impaired Plexin A3 signaling in vivo.

Conclusions:

• Plexin A3 homodimers possess multiple, independent TM and JM interfaces.
• These interfaces collectively regulate dimerization, which is essential for Plexin A3 signal transduction.
• Findings clarify the structural basis of plexin receptor activation.