Mutations in Homocysteine Metabolism Genes Increase Keratin N-Homocysteinylation and Damage in Mice

Kamila Borowczyk; Jacek Wróblewski; Joanna Suliburska; Noriyuki Akahoshi; Isao Ishii; Hieronim Jakubowski

doi:10.1155/2018/7570850

Mutations in Homocysteine Metabolism Genes Increase Keratin N-Homocysteinylation and Damage in Mice

Int J Genomics. 2018 Sep 23:2018:7570850. doi: 10.1155/2018/7570850. eCollection 2018.

Authors

Kamila Borowczyk^{1

2}, Jacek Wróblewski^{3

4}, Joanna Suliburska⁵, Noriyuki Akahoshi⁶, Isao Ishii⁶, Hieronim Jakubowski^{1

4}

Affiliations

¹ Department of Microbiology, Biochemistry and Molecular Genetics, Rutgers-New Jersey Medical School, International Center for Public Health, Newark, NJ 07103, USA.
² Department of Environmental Chemistry, Faculty of Chemistry, University of Łódź, 90-236 Łódź, Poland.
³ Institute of Bioorganic Chemistry, 71-704 Poznań, Poland.
⁴ Department of Biochemistry and Biotechnology, Poznań University of Life Sciences, 60-632 Poznań, Poland.
⁵ Institute of Human Nutrition and Dietetics, Poznań University of Life Sciences, 60-632 Poznań, Poland.
⁶ Department of Health Chemistry, Showa Pharmaceutical University, Tokyo 194-8543, Japan.

Abstract

Genetic or nutritional deficiencies in homocysteine (Hcy) metabolism increase Hcy-thiolactone, which causes protein damage by forming isopetide bonds with lysine residues, generating N-Hcy-protein. In the present work, we studied the prevalence and genetic determinants of keratin damage caused by homocysteinylation. We found that in mammals and birds, 35 to 98% of Hcy was bound to hair keratin via amide or isopeptide bond (Hcy-keratin), while 2 to 65% was S-Hcy-keratin. A major fraction of hair Hcy-keratin (56% to 93%), significantly higher in birds than in mammals, was sodium dodecyl sulfate-insoluble. Genetic hyperhomocysteinemia significantly increased N-Hcy-keratin levels in the mouse pelage. N-Hcy-keratin was elevated 3.5-, 6.3-, and 11.7-fold in hair from Mthfr ^-/-, Cse ^-/-, or Cbs ^-/- mice, respectively. The accumulation of N-Hcy in hair keratin led to a progressive reduction of N-Hcy-keratin solubility in sodium dodecyl sulfate, from 0.39 ± 0.04 in wild-type mice to 0.19 ± 0.03, 0.14 ± 0.01, and 0.07 ± 0.03 in Mthfr ^-/-, Cse ^-/-, or Cbs ^-/-animals, respectively. N-Hcy-keratin accelerated aggregation of unmodified keratin in Cbs ^-/- mouse hair. Keratin methionine, copper, and iron levels in mouse hair were not affected by hyperhomocysteinemia. These findings provide evidence that pelage keratin is N-homocysteinylated in vivo in mammals and birds, and that this process causes keratin damage, manifested by a reduced solubility.