Elucidating crosstalk mechanisms between phosphorylation and O-GlcNAcylation.

Area of Science:

• Molecular Biology
• Biochemistry
• Proteomics

Background:

• Posttranslational modifications (PTMs) create a complex code regulating protein function.
• Understanding PTM interplay is crucial for deciphering cellular processes.
• Phosphorylation and O-GlcNAcylation are common PTMs with largely unknown crosstalk mechanisms.

Purpose of the Study:

• To investigate the crosstalk between phosphorylation and O-GlcNAcylation.
• To identify specific molecular mechanisms governing their interplay.
• To predict and validate novel substrates for O-GlcNAc transferase (OGT).

Main Methods:

• Mass spectrometry-based assays were employed.
• Analysis of the human (phospho)proteome for PTM motifs.
• Experimental validation of predicted OGT substrates.

Main Results:

• Two generic crosstalk mechanisms between phosphorylation and O-GlcNAcylation were demonstrated.
• A stringent motif (pSp/T)P(V/A/T)(gS/gT) was identified, where phosphorylation inhibits O-GlcNAcylation.
• Hundreds of putative OGT substrates were predicted, with experimental validation confirming negative feedback loops.

Conclusions:

• The identified PTM crosstalk motif provides a framework for understanding protein regulation.
• This discovery significantly expands the known landscape of OGT substrates.
• The findings offer insights into the complex regulatory network governed by PTMs.