Reciprocal keratin 18 Ser48 O-GlcNAcylation and Ser52 phosphorylation using peptide analysis.
Phosphorylation and O-GlcNAcylation of keratin 18 (K18) are highly dynamic and involve primarily independent K18 populations. We used in vitro phosphorylation and O-GlcNAcylation of wild-type, phospho-Ser52, glyco-Ser48, and Ser-to-Ala mutant 17mer peptides (K18 amino acids 40-56), which include the major K18 glycosylation (Ser48) and phosphorylation (Ser52) sites, to address whether each modification blocks the other. The glyco-K18 peptide blocks Ser52 phosphorylation by protein kinase C, an in vivo K18 kinase, while the phospho-K18 peptide blocks its O-GlcNAcylation. Our findings support the reciprocity of these two post-translational modifications. Therefore, regulation of protein Ser/Thr phosphorylation and glycosylation at proximal sites can be interdependent and provides a potential mechanism of counter regulation.
Tao
Guo-Zhong
GZ
Palo Alto VA Medical Center, Stanford University, Palo Alto, CA 94304, USA.
Kirby
Celeste
C
Whelan
Stephen A
SA
Rossi
Frank
F
Bi
Xiahui
X
MacLaren
Michael
M
Gentalen
Erik
E
O'Neill
Roger A
RA
Hart
Gerald W
GW
Omary
M Bishr
MB
D000215:Acylation; D019943:Amino Acid Substitution; D005998:Glycine / Q000737:chemistry*; D053538:Keratin-18 / Q000737:chemistry*; D010455:Peptides / Q000737:chemistry; D010766:Phosphorylation; D012694:Serine / Q000737:chemistry*; D013329:Structure-Activity Relationship
D053538:Keratin-18; D010455:Peptides; D012694:Serine; D005998:Glycine