Hyaluronate is synthesized at plasma membranes

Area of Science:

• Biochemistry
• Cell Biology
• Glycobiology

Background:

• The B6 cell line synthesizes hyaluronate as its primary glycosaminoglycan.
• Hyaluronate is a crucial component of the extracellular matrix with significant biological roles.

Purpose of the Study:

• To investigate the synthesis and localization of hyaluronate in B6 cells.
• To elucidate the role of extracellular enzymes in hyaluronate chain elongation and degradation.

Main Methods:

• B6 cells were cultured with radiolabeled precursors ([3H]glucosamine, UDP-GlcNAc, UDP-[14C]GlcA).
• High molecular weight hyaluronate was assessed using Sephacryl S-1000 exclusion chromatography.
• In vitro chain elongation assays were performed after cell disruption.
• Enzymatic treatment with hyaluronidase was employed to study degradation pathways.

Main Results:

• Newly synthesized [3H]hyaluronate exhibited high molecular weight and was excluded by Sephacryl S-1000.
• In vitro incubation allowed for elongation of existing [3H]hyaluronate chains with labeled UDP-GlcNAc and UDP-[14C]GlcA.
• Pre-treatment with hyaluronidase removed high molecular weight hyaluronate.
• Elongation in vitro then initiated from low molecular weight chains.

Conclusions:

• Nascent hyaluronate chains are synthesized intracellularly, likely on the inner side of plasma membranes.
• These chains are subsequently extruded to the cell surface.
• Extracellular hyaluronidase activity leads to the degradation of newly synthesized hyaluronate chains.