Tyrosine O-sulfate ester in proteoglycans.

Area of Science:

• Biochemistry
• Cell Biology
• Proteoglycan Research

Background:

• Proteoglycans are complex macromolecules involved in various biological processes.
• Sulfation is a key post-translational modification of proteoglycans.
• The specific site and timing of tyrosine sulfation in proteoglycans remain areas of investigation.

Purpose of the Study:

• To investigate the presence and extent of tyrosine O-sulfate residues in proteoglycans.
• To determine the role of tyrosine sulfation in proteoglycan biosynthesis.
• To compare tyrosine sulfation levels in cultured cells versus native tissues.

Main Methods:

• Incubation of cultured skin fibroblasts and arterial smooth muscle cells with [35S]sulfate.
• Isolation and analysis of dermatan sulfate proteoglycan and chondroitin sulfate proteoglycan.
• [3H]Tyrosine labeling of fibroblast proteoglycans.
• Pulse-chase experiments to study the timing of tyrosine sulfation.
• Analysis of proteoglycans from cultured cells and arterial tissue.

Main Results:

• Tyrosine O-sulfate residues were detected in the protein core of sulfated proteoglycans.
• Tyrosine sulfation accounted for 0.03%-0.82% of incorporated 35S radioactivity.
• The stoichiometry of tyrosine sulfation varied between cell types and tissues.
• Tyrosine sulfation was identified as a late event in proteoglycan biosynthesis, preceding secretion.
• A tyrosine-sulfated, glycosaminoglycan-free protein core was observed in fibroblasts from a patient with a progeroid variant.

Conclusions:

• Tyrosine O-sulfation is a significant post-translational modification of proteoglycans.
• This modification occurs late in the biosynthetic pathway and is independent of glycosaminoglycan chain synthesis.
• Differences in tyrosine sulfation levels exist between cultured cells and native tissues, suggesting potential regulatory mechanisms.