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Gap junctions were first described as close appositions as other tight junctions, but following electron microscopy studies in 1967, they were renamed gap junctions to distinguish them from tight junctions. [2] They bridge a 2-4 nm gap between cell membranes. [3] Gap junctions use protein complexes known as connexons to
Connexins are commonly named according to their molecular weights, e.g. Cx26 is the connexin protein of 26 kDa. A competing nomenclature is the gap junction protein system, where connexins are sorted by their α (GJA) and β (GJB) forms, with additional connexins grouped into the C, D and E groupings, followed by an identifying number, e.g. GJA1 corresponds to Cx43.
Gap junctions are collections of intercellular channels that allow ions and other tiny molecules to move directly between cells. [1] [14] These junctions are made up of a number of gap junction channels that consist of two connexons, each with six protein subunits called connexin, and a gene family of nearly 20 members encodes the connexins found in mammals [14] [15]
Gap junctions are often present at nerve endings such as in cardiac muscle and are important in maintaining homeostasis in the liver and proper function of the kidneys. The gap junction itself is a structure that is a specialized transmembrane protein formed by a connexon hemichannel. [8]
The permeability of these junctions is dependent on a variety of factors including protein makeup of that junction, tissue type and signaling from the cells. [1] Tight junctions are made up of many different proteins. The four main transmembrane proteins are occludin, claudin, junctional adhesion molecules (JAMs) and tricellulins. The ...
Gap junctions play vital roles in the human body, [11] including their role in the uniform contractile of the heart muscle. [11] They are also relevant in signal transfers in the brain, and their absence shows a decreased cell density in the brain. [12] Retinal and skin cells are also dependent on gap junctions in cell differentiation and ...
Gap junction alpha-1 protein (GJA1), also known as connexin 43 (Cx43), is a protein that in humans is encoded by the GJA1 gene on chromosome 6. [5] [6] [7] As a connexin, GJA1 is a component of gap junctions, which allow for gap junction intercellular communication (GJIC) between cells to regulate cell death, proliferation, and differentiation. [8]
Gap junctions play an important regulatory role in various physiological processes including signal propagation in cardiac muscles and tissue homeostasis of the liver. Modulation is required, since gap junctions must respond to their environment, whether through an increased expression or permeability.