CHKA (choline kinase alpha)

2008-04-01 Ana Ramírez de Molina , María Álvarez-Miranda , Juan Carlos Lacal Affiliation

Centro Nacional de Biotecnologia (CNB), Darwin 3, 28049 Madrid, Spain

Identity

HGNC

CHKA

LOCATION

11q13.2

LOCUSID

1119

ALIAS

CHK,CK,CKI,EK

FUSION GENES

Show Gene Fusions

DNA/RNA

Transcription

The DNA sequence contains 6 exons and the length is of 1374 nt translated to a 457 residues protein.

Proteins

Description

Choline Kinase alpha (CHKA, though we have proposed to name it as ChoKα in order to distinguish it from check point kinase CHK) encodes two different isoforms. Choline Kinase alpha isoform a (ChoKαa) has 457 amino acid residues with a molecular mass of approximatively 52 kDa. Choline Kinase alpha isoform b (ChoKαb) has the same N- and C-termini but is shorter compared to isoform a, resulting in a variant of 439 amino acids and a molecular mass of approximatively 50 kDa.
Both isoforms are active only in an oligomeric form (di- or tetrameric) and require ATP and Mg2+ for their catalytic activity (Wittenberg and Kornberg 1953).

ChoKα structure:
Choline Kinase alpha isoform a (NM_001277) has been crystallized in complex with ADP and phosphocholine (referred in the paper as Choline Kinase alpha2). ATP binds in a cavity where residues from both de N and C-terminal lobes contribute to form a cleft, while the choline-binding site constitutes a deep hydrophobic groove in the C-terminal domain with a rim composed of negative charged residues. Upon binding of choline, the enzyme undergoes conformational changes independently affecting the N-terminal domain and the ATP binding loop (Malito et al. 2006).

ChoKα regulation:
Although much work has been made in other organisms (Paddon et al. 1982; Warden and Friedkin 1985; Kim and Carman 1999; Ramirez de Molina et al. 2002; Yu et al. 2002; Choi et al. 2005; Soto 2008), little is known about human ChoKα regulation.
It has been described that in HeLa cells, both EGF and insulin increase ChoK activity promoting the conversion of Cho to PCho, accompanied by an expansion of the PCho pool in treated cells (Uchida 1996). On the other hand, it has been suggested that Hypoxia-Inducible Factor-1α (HIF-1α) regulates ChoKα expression in a human prostate cancer model. An increase in cellular PCho and total Cho, as well as ChoK expression, has been observed following exposure of PC-3 cells to hypoxia. Furthermore, HIF-1α can directly bind to some putative hypoxia response elements (HRE) within ChoKα promoter, suggesting that HIF-1α activation of HREs within the putative ChoKα promoter region can increase ChoKα expression in hypoxic environments (Glunde et al. 2008).

Expression

Choline Kinase is expressed ubiquitously and concurrently (Aoyama et al. 2002). It is a vital enzyme, as homozygous ChoKa knock-out mice are lethal, indicating the indispensable role of ChoKα in early embryogenesis (Wu et al. 2008).

Localisation

ChoKα is found in the cytoplasm.

Function

Choline Kinase activation is necessary for membranes maintenance, cell growth and cell proliferation. It is also necessary for restoring phospholipids degraded during signal transduction. Consequently, ChoKα has an essential role in growth control and signal transduction and it has been implicated in the carcinogenic process.

Role in metabolic process:
Choline Kinase is the first enzyme in the Kennedy pathway, responsible for de novo synthesis of phosphatidylcholine (PC), one of the major lipid components of plasma membranes in mammal cells, that is also essential for structural stability and cell proliferation. The Kennedy pathway consists of four steps. First Choline Kinase catalyzes choline phosphorylation, then phosphocholine (PCho) cytidylyl-transferase (CCT) catalyzes the formation of CDP-choline from PCho and CTP, and cholinephosphotransferase (CPT) catalyzes the final condensation reaction of CDP-choline with diacylglycerol (DAG) to generate PC. Finally, Phospholipase D (PLD) catalyses the hydrolysis of PC to generate phosphatidic acid (PA) and free choline.
ChoKα can also function as an ethanolamine kinase (EtnK) as it is able to phosphorylate ethanolamine. For a long time choline kinase and ethanolamine kinase have been considered as the same enzyme, because ChoK preparations of highly purified or recombinant enzymes from mammalian sources has been shown to have also a significant EtnK activity. Subsequently, separate genes that would encode EtnK-specific enzymes were identified (Aoyama et al. 2004).

Role in signal transduction, precursor of second messengers:
PC hydrolysis has been implicated in cell signalling. Due to the relative abundance of PC, its hydrolysis can sustain a prolonged liberation of catabolites without drastic changes in membrane phospholipids content. These long-lasting signals are thought to be important in the acquisition of the transformed phenotype. Under mitogenic stimulation by growth factors or oncogenic transformation, PLD-driven PC hydrolysis gives choline and phosphatidic acid (PA). PA can be hydrolyzed or deacylated to form DAG or lysophosphatidic acid (LPA) respectively, both with mitogenic activity. On the other hand, PCho generated from Cho by ChoK is an essential event for growth factors such as platelet-derived growth factor (PDGF) or fibroblast growth factor (FGF). Furthermore, it has been suggested a mitogenic role for PCho (Lacal 2001; Janardhan et al. 2006).

Role in the regulation of cell proliferation:
The accumulation of PC is necessary for the entrance of S phase of the cycle and cell division. It has been recently proposed that ChoKα participates in the regulation of G1-->S transition of the cell cycle at different levels (Ramirez de Molina et al. 2004). ChoKα over-expression induces the transcriptional regulation of genes involved in cell cycle such as p21, p27, and Cyclin D1 and Cyclin D3, whereas ChoKα specific inhibition reverses this effect on the regulation of cell cycle promoting genes. These results suggest the existence of ChoKα-driven co-regulated mechanism to maintain cell growth through the activation of G1-->S transition of the cell cycle (Ramirez de Molina et al. 2008).

Role in carcinogenesis:
PCho is an important lipid metabolite that is involved in cell proliferation as well as in tumorogenesis (Glunde et al. 2006). A role for ChoK in generation of human tumours has been reported. Studies with nuclear magnetic resonance (NMR) reveals elevated levels of PCho in human tumoral tissues in comparison with normal ones (Ruiz-Cabello and Cohen 1992; Smith et al. 1993). The generation of PCho through Kennedy pathway is considered to be one of the crucial steps in regulating growth factor stimulated cell proliferation, malignant transformation, invasion and metastasis (Lacal 2001; Rodriguez-Gonzalez et al. 2003; Glunde et al. 2006). Confirming the role of ChoK in the generation of PCho in the carcinogenic process, this enzyme has been recently described as a novel oncogene that potentiates the tumorogenic ability of other oncogenes such as RhoA (Ramirez de Molina et al. 2005).
ChoKα is over-expressed in different tumour-derived cell lines as well as in different human tumours including breast, lung, prostate and colorectal colon cancers (Ramirez de Molina et al. 2002; Ramirez de Molina et al. 2002). In addition to ChoKα over-expression, an increased enzymatic activity has been observed in human tumours such as breast (Ramirez de Molina et al. 2002) and colon cancer (Nakagami et al. 1999). Furthermore, ChoKα has been recently described as a new prognostic factor to predict patient outcome in early-stage non-small-cell lung cancer patients (Ramirez de Molina et al. 2007).
Consequently, ChoKα inhibition constitutes an efficient antitumour strategy with demonstrated antiproliferative activity in vitro and antitumoral activity in vivo (Hernandez-Alcoceba et al. 1997; Hernandez-Alcoceba et al. 1999). A dramatic difference in the response to MN58b, a specific ChoK inhibitor, has been observed between normal and tumour cells. Whereas blockage of de novo PCho synthesis by MN58b in primary cells induces pRb dephosphorylation and results in reversible cell cycle arrest in G0/G1 phase, tumour cells suffer a drastic wobble in the metabolism of main membrane lipids PC and sphingomyelin, resulting in a significant increase in the intracellular levels of ceramides that promotes cells to apoptosis (Rodriguez-Gonzalez et al. 2003; Rodriguez-Gonzalez et al. 2004; Rodriguez-Gonzalez et al. 2005).

Mutations

Note

No mutations has been described in ChoKα.

Implicated in

Entity name

Breast carcinoma

Oncogenesis

Normal and tumoral tissues from patients with breast carcinomas were analysed for ChoKα activity and expression. ChoKα activity was increased in 38.5% of tumoral tissues, whereas ChoKα over-expression determined by WB analysis was found in 17% of the 53 samples analysed (Ramirez de Molina et al, 2002).

Entity name

Ovarian carcinoma

Oncogenesis

Choline Kinase activity in human epithelial ovarian carcinoma cells (EOC) was 12- to 24-fold higher when compared with normal or immortalized ovary epithelial cells (EONT) (Iorio et al, 2005).

Entity name

Lung cancer

Oncogenesis

ChoKα mRNA levels were increased in lung tumour cell lines in comparison with human primary bronchial epithelial cells (BEC). This increase was higher in small-cell lung cancer (SCLC) than in non-small-cell lung cancer (NSCLC). Moreover, protein levels and ChoK enzymatic activity were also increased in tumour cells (Ramirez de Molina et al, 2007).
When analysing tissues from patients with NSCLC, ChoKα over-expression was also observed with an incidence of 50%. Furthermore, patients with NSCLC with ChoKα over-expression had worse disease free and overall survival than those patients with normal levels of the enzyme (Ramirez de Molina et al, 2007).

Entity name

Colorectal cancer

Oncogenesis

Both ChoKα activity and PCho levels were increased in colon cancer and adenocarcinoma tissues when compared with normal tissue. PCho levels in colon cancers were about 1.5 times higher than in normal colon tissue, whereas ChoK activity was 3.7 times higher in tumoral tissues with respect to normal ones (Nakagami et al, 1999).

Entity name

Prostate cancer

Oncogenesis

Increased ChoKα was found in 48% tumoral prostate tissues when compared with their normal counterparts (Ramirez de Molina et al, 2002).

Bibliography

Pubmed ID	Last Year	Title	Authors
15003397	2004	Structure and function of choline kinase isoforms in mammalian cells.	Aoyama C et al
11964179	2002	Expression and characterization of the active molecular forms of choline/ethanolamine kinase-alpha and -beta in mouse tissues, including carbon tetrachloride-induced liver.	Aoyama C et al
15919656	2005	Phosphorylation of the yeast choline kinase by protein kinase C. Identification of Ser25 and Ser30 as major sites of phosphorylation.	Choi MG et al
17009848	2006	Choline phospholipid metabolism in cancer: consequences for molecular pharmaceutical interventions.	Glunde K et al
18172309	2008	Hypoxia regulates choline kinase expression through hypoxia-inducible factor-1 alpha signaling in a human prostate cancer model.	Glunde K et al
10397253	1999	In vivo antitumor activity of choline kinase inhibitors: a novel target for anticancer drug discovery.	Hernández-Alcoceba R et al
16230400	2005	Alterations of choline phospholipid metabolism in ovarian tumor progression.	Iorio E et al
16719778	2006	Choline kinase: an important target for cancer.	Janardhan S et al
10092638	1999	Phosphorylation and regulation of choline kinase from Saccharomyces cerevisiae by protein kinase A.	Kim KH et al
16015482	2001	Choline kinase: a novel target for antitumor drugs.	Lacal JC et al
17007874	2006	Elucidation of human choline kinase crystal structures in complex with the products ADP or phosphocholine.	Malito E et al
10363580	1999	Increased choline kinase activity and elevated phosphocholine levels in human colon cancer.	Nakagami K et al
6275901	1982	Diethylstilbestrol treatment increases the amount of choline kinase in rooster liver.	Paddon HB et al
18296102	2008	Choline kinase as a link connecting phospholipid metabolism and cell cycle regulation: implications in cancer therapy.	Ramírez de Molina A et al
15753995	2005	Inhibition of choline kinase renders a highly selective cytotoxic effect in tumour cells through a mitochondrial independent mechanism.	Rodríguez-González A et al
1449961	1992	Phospholipid metabolites as indicators of cancer cell function.	Ruiz-Cabello J et al
8268064	1993	Phospholipid metabolites, prognosis and proliferation in human breast carcinoma.	Smith TA et al
18276583	2008	Regulation of the Saccharomyces cerevisiae CKI1-encoded choline kinase by zinc depletion.	Soto A et al
8954133	1996	Stimulation of phospholipid synthesis in HeLa cells by epidermal growth factor and insulin: activation of choline kinase and glycerophosphate acyltransferase.	Uchida T et al
2987212	1985	Regulation of choline kinase activity and phosphatidylcholine biosynthesis by mitogenic growth factors in 3T3 fibroblasts.	Warden CH et al
13061469	1953	Choline phosphokinase.	WITTENBERG J et al
18029352	2008	Early embryonic lethality caused by disruption of the gene for choline kinase alpha, the first enzyme in phosphatidylcholine biosynthesis.	Wu G et al
12105205	2002	Phosphorylation of Saccharomyces cerevisiae choline kinase on Ser30 and Ser85 by protein kinase A regulates phosphatidylcholine synthesis by the CDP-choline pathway.	Yu Y et al

Other Information

Locus ID:

NCBI: 1119
MIM: 118491
HGNC: 1937
Ensembl: ENSG00000110721

Variants:

dbSNP: 1119
ClinVar: 1119
TCGA: ENSG00000110721
COSMIC: CHKA

RNA/Proteins

Gene ID	Transcript ID	Uniprot
ENSG00000110721	ENST00000265689	P35790
ENSG00000110721	ENST00000356135	P35790
ENSG00000110721	ENST00000525155	H0YD02
ENSG00000110721	ENST00000531341	E9PM06

Expression (GTEx)

100

150

Adipose - Subcutaneous

Adipose - Visceral

Adrenal Gland

Artery - Aorta

Artery - Tibial

Bladder

Brain - Amygdala

Brain - Anterior cingulate cortex

Brain - Caudate

Brain - Cerebellar Hemisphere

Brain - Cerebellum

Brain - Cortex

Brain - Frontal Cortex

Brain - Hippocampus

Brain - Hypothalamus

Brain - Nucleus accumbens

Brain - Putamen

Brain - Spinal cord

Brain - Substantia nigra

Breast - Mammary Tissue

Cells - Cultured fibroblasts

Cells - EBV - transformed lymphocytes

Cervix - Ectocervix

Cervix - Endocervix

Colon - Sigmoid

Colon - Transverse

Esophagus - Gastroesophageal Junction

Esophagus - Mucosa

Esophagus - Muscularis

Fallopian Tube

Heart - Atrial Appendage

Heart - Left Ventricle

Kidney - Cortex

Kidney - Medulla

Liver

Lung

Minor Salivary Gland

Muscle - Skeletal

Nerve - Tibial

Ovary

Pancreas

Pituitary

Prostate

Skin - Not Sun Exposed

Skin - Sun Exposed

Small Intestine - Terminal Ileum

Spleen

Stomach

Testis

Thyroid

Uterus

Vagina

Whole Blood

Pathways

Pathway	Source	External ID
Glycerophospholipid metabolism	KEGG	ko00564
Glycerophospholipid metabolism	KEGG	hsa00564
Metabolic pathways	KEGG	hsa01100
Phosphatidylcholine (PC) biosynthesis, choline => PC	KEGG	hsa_M00090
Phosphatidylethanolamine (PE) biosynthesis, ethanolamine => PE	KEGG	hsa_M00092
Phosphatidylcholine (PC) biosynthesis, choline => PC	KEGG	M00090
Phosphatidylethanolamine (PE) biosynthesis, ethanolamine => PE	KEGG	M00092
Choline metabolism in cancer	KEGG	hsa05231
Choline metabolism in cancer	KEGG	ko05231
Metabolism	REACTOME	R-HSA-1430728
Metabolism of lipids and lipoproteins	REACTOME	R-HSA-556833
Phospholipid metabolism	REACTOME	R-HSA-1483257
Glycerophospholipid biosynthesis	REACTOME	R-HSA-1483206
Synthesis of PE	REACTOME	R-HSA-1483213
Synthesis of PC	REACTOME	R-HSA-1483191

Protein levels (Protein atlas)

Not detected

Low

Medium

High

PharmGKB

Entity ID	Name	Type	Evidence	Association	PK	PD	PMIDs
PA443890	Diabetes Mellitus, Type 2	Disease	Literature, MultilinkAnnotation	associated			24595071

References

Pubmed ID	Year	Title	Citations
12176020	2002	Overexpression of choline kinase is a frequent feature in human tumor-derived cell lines and in lung, prostate, and colorectal human cancers.	103
12082619	2002	Increased choline kinase activity in human breast carcinomas: clinical evidence for a potential novel antitumor strategy.	89
18172309	2008	Hypoxia regulates choline kinase expression through hypoxia-inducible factor-1 alpha signaling in a human prostate cancer model.	69
19855431	2010	Selective inhibition of choline kinase simultaneously attenuates MAPK and PI3K/AKT signaling.	47
23071593	2012	Choline kinase alpha and hexokinase-2 protein expression in hepatocellular carcinoma: association with survival.	40
19915674	2009	Differential role of human choline kinase alpha and beta enzymes in lipid metabolism: implications in cancer onset and treatment.	39
11840339	2002	Regulation of choline kinase activity by Ras proteins involves Ral-GDS and PI3K.	36
20042122	2009	Regulation of Akt(ser473) phosphorylation by choline kinase in breast carcinoma cells.	31
18296102	2008	Choline kinase as a link connecting phospholipid metabolism and cell cycle regulation: implications in cancer therapy.	28
25267063	2014	Alterations of choline phospholipid metabolism in endometrial cancer are caused by choline kinase alpha overexpression and a hyperactivated deacylation pathway.	27

Citation

Ana Ramírez de Molina ; María Álvarez-Miranda ; Juan Carlos Lacal

CHKA (choline kinase alpha)

Atlas Genet Cytogenet Oncol Haematol. 2008-04-01

Online version: http://atlasgeneticsoncology.org/gene/44009/chka-(choline-kinase-alpha)