Interaction of arsenic with gap junction protein connexin 43 alters gap junctional intercellular communication

Abstract

Chronic exposure to Arsenic pollution in ground water is one of the largest environmental health disasters in the world. The toxicity of trivalent Arsenicals primarily happens due to its interaction with sulfhydryl groups in proteins. Arsenic binding to the protein can change the conformation of the protein and alter its interactions with other proteins leading to tissue damage. Therefore, much importance has been given to the studies of Arsenic bound proteins, for the purpose of understanding the origins of toxicity and to explore therapeutics. Here we study the dynamic effect of Arsenic on Connexin 43 (Cx43), a protein that forms the gap junctions, whose alteration deeply perturbs the cell-to-cell communication vital for maintaining tissue homeostasis. In silico molecular modelling and in vitro studies comparing Arsenic treated and untreated conditions show distinct results. Gap junction communication is severely disrupted by Arsenic due to reduced availability of unaltered Cx43 in the membrane bound form. In silico and Inductively Coupled Plasma Mass Spectrometry studies revealed the interaction of Arsenic to the Cx43 preferably occurs through surface exposed cysteines, thereby capping the thiol groups that form disulfide bonds in the tertiary structure. This leads to disruption of Cx43 oligomerization, and altered Cx43 is incompetent for transportation to the membrane surface, often forming aggregates primarily localizing in the endoplasmic reticulum. Loss of functional Cx43 on the cell surface have a deleterious effect on cellular homeostasis leading to selective vulnerability to cell death and tissue damage.

Functional and structural phenotyping of cardiomyocytes in the 3D organization of embryoid bodies exposed to arsenic trioxide

“…To this regard, significant enhancement of the expression profiles of Cx40 , Cx43 and Cx45 connexin genes and of Cx43 protein, paralleled by large Cx43 immunofluorescence signals, might contribute to the remodeling of gap junctions leading to abnormal cardiomyocyte conduction properties. In support of our hypothesis, structural model studies showed that arsenic can directly bind to Cx43 channels potentially causing conformational changes in their structure 34 . However, on the basis of our results, we cannot determine whether enhancement of connexins expression is a result or a cause of changed contraction, or even an unrelated effect.…”

Azadirachta indica A. Juss Ameliorates Mouse Hepatitis Virus-Induced Neuroinflammatory Demyelination by Modulating Cell-to-Cell Fusion in an Experimental Animal Model of Multiple Sclerosis

“…The media was discarded, cells were washed with 1 × PBS and 200 µl of fresh media containing (5 mg/ml) of MTT (Thiazolyl Blue Tetrazolium Bromide) was added to each well and incubated at 37 • C with 5% CO 2 for 5 h. The entire solution was discarded carefully without disturbing the purple-colored formazan crystals formed on the surface of the well. Hundred micro-liter of DMSO was added to each well, and absorbance was measured at 570 nm using an Absorbance Plate Reader (Hussain et al, 2018). Net survival values were calculated and plotted using GraphPad Prism 6.0., Maximum non-cytotoxic concentration (MNCC) dose and effective concentration (EC 50 ) of NBE were determined in Neuro-2A cells.…”

GJA1-20k and Mitochondrial Dynamics

“…After Cx43 translation and post-translational modification in the endoplasmic reticulum (ER), Cx43 oligomerizes into hexamers as gap junction hemichannels in the Trans-Golgi Network (TGN) ( Musil and Goodenough, 1993 ; Hussain et al, 2018 ). The hemichannels are then trafficked to cell membrane at cell-cell borders along microtubule “highways” ( Shaw et al, 2007 ; Basheer and Shaw, 2016 ).…”