PTPsigma promotes retinal neurite outgrowth non-cell-autonomously

Area of Science:

• Neuroscience
• Cell Biology
• Developmental Biology

Background:

• Receptor-like protein tyrosine phosphatases (RPTPs) like PTPsigma are crucial for neural development.
• While PTPsigma's cell-autonomous roles are known, non-cell-autonomous functions in axon development are suggested.
• Understanding PTPsigma's signaling is key to axon growth and targeting.

Purpose of the Study:

• To investigate the non-cell-autonomous signaling functions of PTPsigma ectodomains.
• To identify the molecular mechanisms and receptors involved in PTPsigma-mediated neurite outgrowth.
• To explore the role of heparin and its derivatives in modulating PTPsigma activity.

Main Methods:

• Utilized purified PTPsigma ectodomains as a cell culture substrate.
• Assessed retinal neurite outgrowth in response to the PTPsigma substrate.
• Investigated the requirement of PTPsigma's basic amino acid domain and heparin binding properties.
• Tested the inhibitory effects of heparin and oligosaccharide derivatives.

Main Results:

• Purified PTPsigma ectodomains significantly support retinal neurite outgrowth in vitro.
• A specific receptor for PTPsigma exists on retinal axons, independent of its known heparin-binding properties.
• A basic amino acid domain within PTPsigma is essential for its neurite-promoting activity.
• Heparin and short heparin oligosaccharides (8mers) specifically block PTPsigma-mediated neurite outgrowth by competing for binding.

Conclusions:

• PTPsigma exhibits a direct non-cell-autonomous, neurite-promoting function.
• Heparin-related oligosaccharides can modulate RPTP-mediated neurite outgrowth.
• This study reveals a novel signaling pathway involving PTPsigma and heparin in axon development.