Lefty Glycoproteins in Human Embryonic Stem Cells: Extracellular Delivery Route and Posttranslational Modification in...

Area of Science:

• Stem cell biology
• Molecular and cell biology
• Cancer research

Background:

• Lefty proteins, part of the TGF-β superfamily, antagonize TGF-β/Nodal/Activin signaling and are crucial for embryonic stem cell (ESC) pluripotency and differentiation.
• The secretion mechanism and glycan significance of Lefty proteins (Lefty A and B) are largely unknown.

Purpose of the Study:

• To investigate the secretion mode of Lefty proteins from human ESCs (hESCs).
• To analyze the proteolytic processing and N-glycan structures of Lefty in different cell types and secretion pathways.
• To assess the functional impact of Lefty modifications on Nodal signaling, particularly in cancer cells.

Main Methods:

• Utilized an in vitro system of hESCs.
• Analyzed cell-associated and exosomal Lefty proteins.
• Characterized N-glycan structures and proteolytic processing.
• Assessed Lefty's inhibitory effect on Nodal signaling in melanoma cells.

Main Results:

• Lefty proteins are secreted within exosomes from hESCs.
• Exosomal and cell-associated Lefty exhibit different proteolytic processing and N-glycan profiles (high mannose and complex types).
• Differentiation of hESCs into mesenchymal stem cells (MSCs) or neuronal progenitor cells (NPCs) alters Lefty gene/protein expression, processing, and glycosylation.
• These modifications influence Lefty's inhibitory activity on Nodal signaling in melanoma cells.

Conclusions:

• Lefty secretion via exosomes is a key mechanism for its extracellular release.
• Microheterogeneity in Lefty processing and glycosylation across different cell types (hESCs, MSCs, NPCs) diversifies its functions.
• Lefty-packaged exosomes hold potential therapeutic relevance for diseases, including cancer.