Disrupting of E79 and K138 interaction is responsible for human muscle creatine kinase deficiency diseases

Roles of amino acid residues H66 and D326 in the creatine kinase activity and structural stability

Creatine kinase (CK) is a key enzyme for cellular energy metabolism, catalyzing the reversible phosphoryl transfer from phosphocreatine to ADP in vertebrates. CK contains a pair of highly conserved amino acids (H66 and D326) which might play an important role in sustaining the compact structure of CK by linking its N- and C- terminal domains; however the mechanism is still unclear. In this study, spectroscopic, structural modeling and protein folding experiments suggested that D326A, H66P and H66P/D326A mutations led to disruption of the hydrogen bond between those two amino acid residues and form the partially unfolded state which made it easier to be inactivated and unfolded under environmental stresses, and more prone to form insoluble aggregates. The formation of insoluble aggregates would decrease levels of active CKs which may provide clues in CK deficiency disease. Moreover, these results indicated that the degree of synergism had closely relationship to the conformational changes of CK. Thus, our results provided clues for understanding the mechanism of amino acid residues outside the active site in regulating substrate synergism.

CKM and LILRB5 are associated with serum levels of creatine kinase

BACKGROUND

Statins (HMG-CoA reductase inhibitors) are the most prescribed class of lipid-lowering drugs for the treatment and prevention of cardiovascular disease. Creatine kinase (CK) is a commonly used biomarker to assist in the diagnosis of statin-induced myotoxicity but the normal range of CK concentrations is wide, which limits its use as a diagnostic biomarker.

METHODS AND RESULTS

We conducted a genome-wide association study of serum CK levels in 3412 statin users. Patients were recruited in Quebec, Canada, and genotyped on Illumina Human610-Quad and an iSelect panel enriched for lipid homeostasis, hypertension, and drug metabolism genes. We found a strong association signal between serum levels of CK and the muscle CK (CKM) gene (rs11559024: P=3.69×10(-16); R(2)=0.02) and with the leukocyte immunoglobulin-like receptor subfamily B member 5 (LILRB5) gene (rs2361797: P=1.96×10(-10); R(2)=0.01). Genetic variants in those 2 genes were independently associated with CK levels in statin users. Results were successfully replicated in 5330 participants from the Montreal Heart Institute Biobank in statin users for CKM (rs11559024: P=4.32×10(-16); R(2)=0.02) and LILRB5 (rs12975366 P=4.45×10(-10); R(2)=0.01) and statin nonusers (P=4.08×10(-7), R(2)=0.01; P=3.17×10(-9), R(2)=0.02, respectively).

CONCLUSIONS

This is the first genome-wide study to report on the underlying genetic determinants of CK variation in a population of statin users. We found statistically significant association for variants in the CKM and LILRB5 genes.