Cell Junction Antibodies

Figure 1—Connexin-40 and Connexin-43. Immunofluorescent staining of mouse heart atrium using mouse anticonnexin-43 antibody (red) and mouse anti-connexin-40 antibody (green). Image courtesy of James I. Nagy, PhD, University of Manitoba, Canada.

Gap junctions are clusters of tightly packed channels that allow small molecules (metabolites, second messengers, and ions) to travel between adjoining cells¹. This molecular exchange is essential during development and differentiation; it also creates cell proliferation, tumor suppression, cell death propagation, and survival-modulating signals². These signals include connexins, and pannexin 1 and 2, important components of synapses^3.. Several kinases phosphorylate connexins and alter their functions: V-src kinase, C-src kinase, PKC, MAPK, cdc2 kinase, casein kinase I, and PKA.

Figure 2. Claudin proteins. Immunofluorescence staining of frozen mouse jejunum tissue using Mouse anti-Claudin-1 (red), and Mouse anti ZO-1 is labeled in green; nuclei are stained with DAPI (blue). Image courtesy of Jennifer Holmes and Dr. James Anderson, University of North Carolina at Chapel Hill, NC.

Tight junctions are barriers that regulate the paracellular movement of solutes down their electro-osmotic gradients. They also act as a fence that maintains differential composition of basolateral and apical membrane domains, limiting the diffusion of lipids and proteins between cellular compartments. The main components of tight junctions are claudins, occludins, and junctional adhesion molecules (JAMs). Proteins such as ZO-1, ZO-2, ZO-3, MUPP-1, and PATJ colocalize with claudin proteins and together form tight junctions (Figure 2). 

Figure 3. Cell junctions. Immunohistochemistry of mouse hippocampus using AF-6 ABfinity™ Recombinant Rabbit Monoclonal Antibody, at 1 μg/mL. Goat anti Rabbit Alexa Fluor® 488 was used as secondary antibody. Image provided by Jim Nagy, Canada.

Adherens junctions are the building blocks of tissue architecture. Their main components are cadherins and catenins. These proteins form cell−cell junctions (Figure 3), and can facilitate signaling pathways such as AKT, Wnt, and MAPK to govern morphogenesis, tissue homeostasis, and intercellular communication^5.. Disruption of adherens junctions promotes tumor cell invasion and metastasis ⁶.