PCK1

What is PCK1 protein?

PCK1 gene (phosphoenolpyruvate carboxykinase 1) is a protein coding gene which situated on the long arm of chromosome 20 at locus 20q13. This gene is a main control point for the regulation of gluconeogenesis. The cytosolic enzyme encoded by this gene, along with GTP, catalyzes the formation of phosphoenolpyruvate from oxaloacetate, with the release of carbon dioxide and GDP. The expression of this gene can be regulated by insulin, glucocorticoids, glucagon, cAMP, and diet. Defects in this gene are a cause of cytosolic phosphoenolpyruvate carboxykinase deficiency. A mitochondrial isozyme of the encoded protein also has been characterized. The PCK1 protein is consisted of 622 amino acids and PCK1 molecular weight is approximately 69.2 kDa.

What is the function of PCK1 protein?

PCK1 is an enzyme that plays a crucial role in gluconeogenesis, the metabolic pathway responsible for generating glucose from non-carbohydrate precursors. Specifically, PCK1 catalyzes the reversible decarboxylation and phosphorylation of oxaloacetate (OAA) to produce phosphoenolpyruvate (PEP), which is considered the rate-limiting step in this metabolic process. Moreover, PCK1 has been found to regulate cataplerosis and anaplerosis, processes that control the levels of metabolic intermediates in the citric acid cycle. In addition to its metabolic role, PCK1 has been implicated in the regulation of memory CD8(+) T-cells. Furthermore, PCK1 has been shown to act as a protein kinase when phosphorylated at Ser-90, which can regulate lipogenesis by affecting the interaction between INSIG proteins and SCAP.

Fig1. Scheme of glycolysis, gluconeogenesis and branching biosynthetic pathways. (Gabriele Grasmann, 2019)

PCK1 Related Signaling Pathway

PCK1 functions as a rate-limiting enzyme in the gluconeogenesis pathway, which is essential for glucose homeostasis. Research indicates that the PPAR-γ-PCK1-mTOR signaling pathway may play a role in the process of islet cell apoptosis induced by hyperuricemia, suggesting a connection between PCK1 and cellular metabolic health. PCK1 has been shown to activate AMP-activated protein kinase (AMPK), which is a key energy sensor in cells. Through its effects on AMPK and the downstream RB/E2F signaling pathway, PCK1 can influence cell cycle progression and potentially impact cell proliferation and tumor growth. PCK1 deficiency has been associated with the activation of the RhoA/PI3K/AKT/PDGF-AA signaling axis, which can promote liver fibrosis, indicating a role for PCK1 in inflammatory processes and tissue repair.

PCK1 Related Diseases

In the context of metabolic diseases, PCK1's dysregulation is linked to conditions such as metabolic associated fatty liver disease (MAFLD), where its deficiency can lead to lipid deposition in hepatocytes and activation of the RhoA/PI3K/AKT/PDGF-AA signaling axis, promoting liver fibrosis. Additionally, PCK1 has been identified as a potential therapeutic target in cancer, where its expression can influence cell growth and proliferation. Furthermore, PCK1's role in angiogenesis has been highlighted in the context of retinal neovascular diseases, such as proliferative diabetic retinopathy (PDR), where it's suggested to play a key role in promoting blood vessel growth.

Bioapplications of PCK1

Research has highlighted PCK1's potential as a biomarker and therapeutic target in diabetes and cancer, with studies demonstrating its involvement in the Warburg effect and its capacity to modulate the tumor microenvironment. Furthermore, PCK1's metabolic activities are crucial for the function of CD8+ memory T cells, which are essential for protective immunity against infections and cancers. The enzyme has also been identified as a regulator of epigenetic modifications, such as histone methylation, which can influence gene expression and cell behavior.

Case Study 1: Yu-Ching Wen, 2022

Castration-resistant prostate cancer (CRPC) patients frequently develop neuroendocrine differentiation, with high mortality and no effective treatment. However, the regulatory mechanism that connects neuroendocrine differentiation and metabolic adaptation in response to therapeutic resistance of prostate cancer remain to be unravelled. By unbiased cross-correlation between RNA-sequencing, database signatures, and ChIP analysis, combining in vitro cell lines and in vivo animal models, researchers identified that PCK1 is a pivotal regulator in therapy-induced neuroendocrine differentiation of prostate cancer through a LIF/ZBTB46-driven glucose metabolism pathway. The results revealed that PCK1 and neuroendocrine marker expressions are regulated by the ZBTB46 transcription factor upon activation of LIF signalling. Targeting PCK1 can reduce the neuroendocrine phenotype and decrease the growth of prostate cancer cells in vitro and in vivo.

Fig1. Representative immunoblots of PCK1, ZBTB46, and LIF protein levels.

Fig2. Representative immunoblots of PCK1 protein levels in cells exposed to nilotinib or lapatinib.

Case Study 2: Pedro Latorre-Muro, 2021

Acetylation is known to regulate the activity of cytosolic phosphoenolpyruvate carboxykinase (PCK1), a key enzyme in gluconeogenesis, by promoting the reverse reaction of the enzyme (converting phosphoenolpyruvate to oxaloacetate). It is also known that the histone acetyltransferase p300 can induce PCK1 acetylation in cells, but whether that is a direct or indirect function was not known. Here researchers initially set out to determine whether p300 can acetylate directly PCK1 in vitro. They report that p300 weakly acetylates PCK1, but surprisingly, using several techniques including protein crystallization, mass spectrometry, isothermal titration calorimetry, saturation-transfer difference nuclear magnetic resonance and molecular docking, researchers found that PCK1 is also able to acetylate itself using acetyl-CoA independently of p300. This reaction yielded an acetylated recombinant PCK1 with a 3-fold decrease in kcat without changes in Km for all substrates.

Fig3. Determination of PCK1 activity.

Fig4. PCK1 was incubated in the presence of only 1 mM of acetyl-CoA or in the presence of other PCK1 substrates.

PCK1 has several biochemical functions, for example, GDP binding,GTP binding,carboxylic acid binding. Some of the functions are cooperated with other proteins, some of the functions could acted by PCK1 itself. We selected most functions PCK1 had, and list some proteins which have the same functions with PCK1. You can find most of the proteins on our site.

PCK1 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 PCK1 here. Most of them are supplied by our site. Hope this information will be useful for your research of PCK1.

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