CKB

What is CKB Protein?

CKB gene (creatine kinase B) is a protein coding gene which situated on the long arm of chromosome 14 at locus 14q32. The protein encoded by this gene is a cytoplasmic enzyme involved in energy homeostasis. The encoded protein reversibly catalyzes the transfer of phosphate between ATP and various phosphogens such as creatine phosphate. It acts as a homodimer in brain as well as in other tissues, and as a heterodimer with a similar muscle isozyme in heart. The encoded protein is a member of the ATP:guanido phosphotransferase protein family. The CKB protein is consisted of 381 amino acids and CKB molecular weight is approximately 42.6 kDa.

What is the Function of CKB Protein?

CKB protein, Creatine Kinase B, is an enzyme that plays an important role in the cytoplasm and belongs to the ATP: guanidine phosphotransferase protein family. It is primarily involved in the regulation of energy homeostasis, which it does by reversibly catalyzing the transfer of phosphate between ATP and various phosphogen (such as creatine phosphate). CKB is expressed in a variety of tissues, especially in the brain and other tissues in the form of homodimers, and in the heart in the form of heterodimers with similar muscle isoenzymes. In addition to its role in energy buffering, CKB also has non-metabolic functions. In addition, CKB controls the meaningless creatine cycle in heat-producing fat, a process that plays an important role in regulating energy expenditure and warding off obesity.

CKB Related Signaling Pathway

CKB inhibits EMT and prostate cancer progression by isolating and inhibiting AKT activation. AKT activation is key to many cellular processes, and downregulation of CKB is associated with poorer prognosis and promotes EMT and cell migration, as well as xenograft tumor growth and metastasis. CKB, as a protein kinase, uses creatine phosphate (pCr) as a phosphate donor to phosphorylate BCAR1 to promote intracellular DNA damage repair. CKB controls the meaningless creatine cycle in thermogenic fat, which is essential for thermogenic and metabolic health of fat cells. CKB reduces the production of glycolytic ATP by inhibiting mitochondrial calcium (mCa2 +) levels, thereby preventing the activation of mitochondrial permeability transition pores (mPTP) and ensuring efficient production of mitochondrial ATP. In liver cancer cells, CKB T133 can be phosphorylated by AKT, causing it to acquire the non-classical function of protein kinase, bind to and phosphorylate GPX4 S104, and improve the defense ability of tumor cells against iron death.

CKB Related Diseases

CKB inhibits iron death of tumor cells and promotes tumor growth by phosphorylation of GPX4. CKB, as a protein kinase, uses creatine phosphate (pCr) as a phosphate donor to phosphorylate BCAR1 to promote intracellular DNA damage repair. CKB is involved in the regulation of cellular energy homeostasis, and its abnormality may be associated with metabolic diseases. Elevated levels of CKB, one of the myocardial enzymes, may indicate myocardial damage or heart disease. CKB, which is expressed in brain tissue, is closely related to nervous system function and may be associated with some neurodegenerative diseases. Statins and other drugs may cause elevated CKB, and it is necessary to pay attention to drug-related muscle side effects.

Fig1. Proposed model for the pathogenesis of hearing impairment in Huntington's disease (HD). (Yow-Sien Lin, 2011)

Bioapplications of CKB

Because CKB protein can inhibit cell proliferation, it is considered as a potential anti-tumor drug target. With age, the ability of cells to regenerate gradually decreases, which is related to the expression level of CKB protein. Therefore, by regulating the expression of CKB protein, it may help to delay the aging process. Studies have shown that CKB protein can inhibit the proliferation of vascular smooth muscle cells, thereby preventing blood vessel narrowing and blockage. Therefore, CKB protein has the potential to be used in the treatment of cardiovascular disease. Similarly, it has potential for drug development in other related diseases.

Case Study 1: Zheng Wang, 2021

The epithelial-mesenchymal transition (EMT) is a cellular process that plays a significant role in tumor invasion, metastasis, and the development of drug resistance. Despite the identification of many positive regulators that promote EMT and AKT activation, there is a scarcity of well-established negative regulators. In a recent study, brain-type creatine kinase (CKB or BCK) emerged as a potent suppressor of both EMT and AKT activation. Overexpression of CKB was observed to inhibit EMT, cell migration, and the growth and metastasis of prostate cancer cells, while its silencing had the opposite effect, promoting these phenotypes. The EMT enhancement caused by CKB silencing was negated by inhibiting AKT. It was discovered that CKB interacts with AKT, preventing its activation by mTOR. Specifically, an 84-amino acid fragment at the C-terminus of the CKB protein was identified to interact with the pleckstrin homology (PH) domain of AKT. The ectopic expression of this 84aa CKB fragment was shown to inhibit AKT activation, EMT, and cell proliferation. Molecular dynamics simulations based on the crystal structures of AKT and CKB provided evidence that the PH domain of AKT and the 84aa fragment of CKB form their primary interaction interface.

Fig1. AKT protein was immunoprecipitated by CKB antibody in a mixture of recombinant His-tagged AKT and His-tagged CKB proteins.

Fig2. The RMSD of Cα atoms of AKT and CKB in 100 ns trajectory.

Case Study 2: Adriana Simionescu-Bankston, 2015

Myoblast fusion is essential for muscle growth and repair. The spatial restriction of certain molecular localizations during this process is observed, but the reasons behind this pattern are not well understood. Creatine kinase B (CKB), an enzyme that replenishes ATP in the vicinity, is found predominantly at the ends of cultured primary mouse myotubes. To explore the role of CKB, researchers conducted a yeast two-hybrid screen to find proteins that interact with CKB and discovered a variety of molecules involved in diverse cellular functions such as actin polymerization, intracellular transport, alternative splicing, and sarcomeric structure formation.
Further investigation into two main muscle actin isoforms, α-skeletal actin, and α-cardiac actin, revealed their biochemical interaction with CKB and partial colocalization at the myotube ends. Unlike in other cells, the specific reduction of CKB did not significantly impact actin polymerization in myotubes, pointing to unique roles for CKB in muscle cells. Notably, the downregulation of CKB led to an increase in both myoblast fusion rates and myotube size in vitro, while the knockdown of creatine kinase M showed no effect on these muscle-specific parameters.

Fig3. Pure cultures of mouse muscle cells were immunostained for CKB or CKM at various stages of myogenesis.

Fig4. CKB and CKM protein expression during myogenesis.

CKB has several biochemical functions, for example, ATP binding,creatine kinase activity,protein binding. Some of the functions are cooperated with other proteins, some of the functions could acted by CKB itself. We selected most functions CKB had, and list some proteins which have the same functions with CKB. You can find most of the proteins on our site.

CKB has direct interactions with proteins and molecules. Those interactions were detected by several methods such as yeast two hybrid, co-IP, pull-down and so on. We selected proteins and molecules interacted with CKB here. Most of them are supplied by our site. Hope this information will be useful for your research of CKB.

ASB9;q03463-pro_0000278738;NFKB2;USPL1;q99ib8-pro_0000045600;USP15;p27958-pro_0000037574;MLH1;TERF1;PPP1CA;ILK