Zona occludens protein 2 (ZO-2), also known as tight junction protein 2 (TJP2), is a membrane-associated guanylate kinase acting at intercellular contacts of epithelial and endothelial cells but also in their nuclei.
What is the molecular weight of ZO-2? Are there any isoforms of ZO-2? Is ZO-2 post-translationally modified?
The molecular weight of ZO-2 is 160 kDa. There are two known isoforms of ZO-2: full-length ZO-2A and ZO-2C lacking the first 23 amino acids (PMID: 10360833). ZO-2 can be phosphorylated and O-glycosylated, which has an impact on its localization (PMID: 23804652).
What is the subcellular localization of ZO-2?
ZO-2 is present at the cytoplasmic face at cell-cell contact sites: tight junctions, adherens junctions, and gap junctions (PMID: 20224657). ZO-2 contains nuclear localization and nuclear export signals and can actively shuttle between the cytoplasm and nucleus (PMID: 11855865). In the nucleus it can affect the activity of various transcription factors. ZO-2 nuclear localization is most prominent in sparse 2D cell cultures and also in cells subjected to mechanical or chemical stress.
What is the tissue expression pattern of ZO-2?
ZO-2 is expressed in various tissues in epithelial and endothelial cells. ZO-2 isoforms have tissue specificity, with ZO-2A being abundant in the heart and brain, while ZO-2C is found in the kidney, pancreas, heart, and placenta (PMID: 11018256).
What proteins can be used as markers of tight junctions?
Zona occludens proteins are often used as tight junction markers. Apart from the antibody against ZO-2, one can use antibodies against ZO-1 (https://www.ptglab.com/products/ZO1-Antibody-21773-1-AP.htm), occludin (https://www.ptglab.com/products/OCLN-Antibody-13409-1-AP.htm), and claudins (e.g., claudin 1: https://www.ptglab.com/products/CLDN1-Antibody-13050-1-AP.htm).