Transmembrane semaphorin5B is proteolytically processed into a repulsive neural guidance cue

Area of Science:

• Neuroscience
• Molecular Biology
• Cell Biology

Background:

• Neuronal growth cones navigate using guidance cues.
• Semaphorins are key guidance cues, acting as secreted or transmembrane proteins.
• Post-transcriptional modifications regulate guidance cue function.

Purpose of the Study:

• To investigate the processing and function of transmembrane Semaphorin 5B (Sema5B).
• To identify proteases involved in Sema5B ectodomain shedding.
• To understand Sema5B's role as a soluble guidance cue.

Main Methods:

• Over-expression and knockdown of A Disintegrin and Metalloprotease (ADAM)-17.
• Site-directed mutagenesis to remove predicted ADAM-17 cleavage site.
• Analysis of Sema5B ectodomain release.

Main Results:

• Transmembrane Sema5B is proteolytically processed into a soluble form.
• Over-expression of ADAM-17 enhances Sema5B ectodomain release.
• Removal of the predicted ADAM-17 cleavage site inhibits release, but other proteases compensate.
• Soluble Sema5B functions as a growth cone collapsing cue.

Conclusions:

• Sema5B can be shed from the cell membrane to act as a soluble guidance cue.
• ADAM-17 contributes to Sema5B processing, but compensatory proteases exist.
• This processing provides a mechanism for regulating neuronal guidance in vivo.