CELL TO CELL NETWORKS

CELL TO CELL NETWORK

Gap Junction: Gap Junctions plays a very important role in cell to cell communication and regulate cell differentiation, cell growth and development. The most important function of Gap Junction Intercellular Communication (GJIC) is to maintain the vascular homeostasis between the cytoplasm of two neighboring cells and to regulate cell survival. This Gap Junction acts just like a transmembrane protein or channel and makes possible the passage of nutrients, ions and small molecules between the two cells. These gap junctions regulate the survival of the cells by exchange of metabolites, ions, glucose, secondary messengers and ATP.

Connexin: Gap junctions are also present in many tissues such as retina in which Connexin 43 (Cx43) is mostly present. Connexins are the family of multigene and many members of this gene is present in the eye. If mutation occurs in the genes that encodes the several members of Connexin family cause many human diseases. In-vitro experiments have revealed that Gap junction activity is affected in the presence of high glucose in pericytes, retinal and microvascular endothelial cells. It is currently reported that 21 isoforms of connexins is present in human genome. A change in the gap junction activity and the expression of Connexin 43 has also been expressed in many diabetic tissues such as diabetic retina, skin, lens epithelium and kidney. Connexon is a connexin subunits and assemble in the form of hexamers. Intercellular channels are described as homotypic and heterotypic. If the molecular composition of two connexins is same it is known as homotypic, or if the molecular composition is different of two connexins it is known as heterotypic. In diabetic retinopathy destruction of the retinal cells causes the retinal lesions in the early stages of diabetic retinopathy. Connexin maintains the vascular function and GJIC activity for example, in growth and development. Connexin also modulates the growth signals. In diabetic condition, the activity of GJIC is reduced which cause the death of retinal endothelail cells and pericytes. Chronic hyperglycemia associated with many pathological changes which lead to the breakdown of retinal blood barriers.

Simplified illustration of extracellular
purinergic signalling

Pannexin: Pannexins are a huge single membrane channels and pannexin gene family contains 3 members such as panx 1, 2 and 3. Pannexin express in many parts of the vertebrate body such as nose, ear or lens etc.Pannexin plays a very important role in the visual system and mainly focused on disease that leading to blindness. The first condition is Age-Related Macular Degeneration (AMD) that condition which leads to the loss of vision. AMD condition is developed when by the progressive destruction of retinal pig-ment epithelial (RPE) cells in the macula, which lead to increased intraocular pressure, and the neovascularization of the subretinal macular region. AMD also cause bleeding and leakage of the fluids from the eye