Specific citrullination causes assembly of a globular S100A3 homotetramer: a putative Ca2+ modulator matures human hair cuticle.
S100A3 is a unique member of the Ca2+-binding S100 protein family with the highest cysteine content and affinity for Zn2+. This protein is highly expressed in the differentiating cuticular cells within the hair follicle and organized into mature hair cuticles. Previous studies suggest a close association of S100A3 with epithelial differentiation, leading to hair shaft formation, but its molecular function is still unknown. By two-dimensional PAGE-Western blot analyses using a modified citrulline antibody, we discovered that more than half of the arginine residues of native S100A3 are progressively converted to citrullines by Ca2+-dependent peptidylarginine deiminases. Confocal immunofluorescent microscopy showed that the cytoplasmic S100A3 within the cuticular layer is mostly co-localized with the type III isoform of peptidylarginine deiminase (PAD3) but not with PAD1. Recombinant PAD1 and PAD2 are capable of converting all 4 arginines in recombinant S100A3, whereas PAD3 specifically converts only Arg-51 into citrulline. Gel filtration analyses showed that either enzymatic conversion of Arg-51 in S100A3 to citrulline or its mutational substitution with alanine (R51A) promotes a homotetramer assembly. Fluorescent titration of R51A suggested that its potential Ca2+ binding property increased during tetramerization. A prototype structural model of the globular Ca2+-bound S100A3 tetramer with citrulline residues is presented. High concentrations of S100A3 homotetramer might provide the millimolar level of Ca2+ required for hair cuticular barrier formation.
Kizawa
Kenji
K
Basic Research Laboratory, Kanebo Cosmetics Inc., 5-3-28 Kotobuki-cho, Odawara 250-0002, Japan. kizawa.kenji@kanebocos.co.jp
Takahara
Hidenari
H
Troxler
Heinz
H
Kleinert
Peter
P
Mochida
Urara
U
Heizmann
Claus W
CW
D019943:Amino Acid Substitution; D002118:Calcium / Q000378:metabolism; D002454:Cell Differentiation / Q000502:physiology; D002956:Citrulline / Q000235:genetics / Q000378:metabolism*; D006197:Hair / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D006867:Hydrolases / Q000235:genetics / Q000378:metabolism*; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D008297:Male; D008958:Models, Molecular; D011499:Protein Processing, Post-Translational / Q000502:physiology*; D020836:Protein Structure, Quaternary / Q000502:physiology; D000080064:Protein-Arginine Deiminase Type 2; D000076342:Protein-Arginine Deiminases; D009418:S100 Proteins / Q000235:genetics / Q000378:metabolism*; D015032:Zinc / Q000378:metabolism
D007527:Isoenzymes; D009418:S100 Proteins; C082356:S100A3 protein, human; D002956:Citrulline; D006867:Hydrolases; C000620352:PADI2 protein, human; D000080064:Protein-Arginine Deiminase Type 2; D000076342:Protein-Arginine Deiminases; D015032:Zinc; D002118:Calcium