Regulation Mechanism of Occludin Function and Factors Affecting Its Expression
10.16476/j.pibb.2024.0164
- VernacularTitle:闭合蛋白功能的调控机制及影响其表达的因素
- Author:
Shi-Jia ZHANG
1
;
Juan-Xia ZHENG
2
;
Cheng-Wei WANG
1
Author Information
1. College of Life Science, Jiangxi Science and Technology Normal University, Nanchang330013, China
2. Guixi Experimental Middle School, Guixi335400, China
- Publication Type:Journal Article
- Keywords:
Occludin;
tight junction;
regulation mechanism;
impactor factors
- From:
Progress in Biochemistry and Biophysics
2024;51(11):2832-2844
- CountryChina
- Language:Chinese
-
Abstract:
Tight-junction (TJ) is a complex supramolecular entity composed of complete membrane proteins, membranes and soluble cytoplasmic proteins, which is distributed in almost all barrier structures in the body. It can maintain the polarity of epithelial cells, close the intercellular space and prevent the overflow of materials in the epithelial space, and is a highly dynamic signaling entity. Occludin is one of the most representative members of TJ proteins, mainly responsible for sealing intercellular connections, maintaining intercellular permeability, and participating in maintaining the integrity of vascular endothelium. The integrity of occludin is related to the integrity of TJ, and the function of occludin is often associated with the barrier properties of various tissues, and the abnormal expression of occludin is related to the occurrence and development of various diseases. Occludin contains abundant Ser and Thr residues and has multiple phosphorylation sites. Phosphorylation is necessary for the combination of occludin and TJ, which can regulate the location of occludin, regulate the expression of occludin, and enhance the permeability and barrier function of TJ. Therefore, phosphorylation regulation is a mechanism that cannot be ignored in the regulation of occludin function. Occludin also interacts with many other proteins, such as co-forming the cytoskeleton with ZO-1, and is regulated by a variety of transcription factors. Studies have confirmed that in pathological conditions, a variety of signaling pathways can disrupt the integrity of cell barrier by regulating the expression and distribution of occludin. Myosin light chain kinase (MLCK) signal transduction pathway is one of the important ways to regulate the structure and function of TJ. It influences the expression of occludin by altering the cytoskeleton. MLCK mainly uses the phosphorylation of myosin light chain (MLC) as a medium to promote actin contraction, secondary decomposition of tightly binding proteins, resulting in increased or changed cellular barrier permeability, and increased MLC phosphorylation is also a biochemical marker of actomyosin contraction. Activation of MLCK causes Thr18 and Ser19 phosphorylation of MLC, which promotes the assembly of myosin II into myosin fibers and activates the hydrolysis of ATP, which relaxes the intercellular connections and reduces the ability of upper cortex to resist external invaders. Protein kinase C (PKC) plays an important role in the regulation of tightly connected signaling molecules, affecting the dynamic changes of paracellular permeability. PKC pathway is a key link in many cell signal transduction pathways, which influences all aspects of cell activities by catalyzing Ser/Thr residues phosphorylation of membrane proteins and many enzyme proteins. After PKC activation, it can regulate cellular barrier function by phosphorylating occludin and inducing its redistribution, and directly affect TJ action. Specific PKC subunits such as PKCα, PKCδ and PKCγ are activated and act on occludin molecules to promote their phosphorylation and cause the increase of TEER. The increase of TEER helps to regulate intercellular TJ and enhance the tightness of intercellular connections. Mitogen-activated protein kinases (MAPK) are usually activated by inflammatory factors, during which different signal transduction pathway subfamilies are formed to regulate occludin expression and affect tight junction and mucosal barrier functional integrity. Meanwhile, occludin is easily affected by various factors (such as cytokines and flora toxins), and abnormal expression of occludin will lead to structural damage of TJ and further damage of the intercellular barrier. Therefore, this paper summarizes the molecular structure and physiological function of occludin, and further summarizes its related signal regulation pathways and influencing factors, in order to provide theoretical support for maintaining the integrity of barrier function of occludin.
