What does the B subunit of cholera toxin do?
The CT B subunit binds to GM1 gangliosides on the surface of intestinal epithelial cells, inducing endocytosis of the toxin and the release of the A subunit, leading to increased adenylate cyclase activity and the secretion of water and electrolytes to the intestinal lumen that can cause profuse, watery diarrhea.
Which lipid is receptor for cholera toxin?
ganglioside GM1
Cholera toxin (CT), and members of the AB5 family of toxins enter host cells and hijack the cell’s endogenous pathways to induce toxicity. CT binds to a lipid receptor on the plasma membrane (PM), ganglioside GM1, which has the ability to associate with lipid rafts.
Are lipid rafts found in the plasma membrane?
Lipid rafts (also known as lipid microdomains) are discrete lipid domains present in the external leaflet of the plasma membrane. The rafts are enriched in cholesterol, glycosphingolipids, and glycosyl-phosphatidylinositol GPI-anchored proteins, and are insoluble in low concentrations of nonionic detergents.
What is the role of lipid rafts in biomembranes?
Lipid rafts, also known as microdomains, are important components of cell membranes and are enriched in cholesterol, glycophospholipids and receptors. They are involved in various essential cellular processes, including endocytosis, exocytosis and cellular signaling.
How does cholera toxin enter cells?
Cholera toxin (CT), an AB5-subunit toxin, enters host cells by binding the ganglioside GM1 at the plasma membrane (PM) and travels retrograde through the trans-Golgi Network into the endoplasmic reticulum (ER).
Which cholera toxin subunit is directly responsible for the increase in adenylate cyclase activity?
The B subunit is responsible for binding to the monoganglioside GM1 receptor on intestinal epithelial cells. The A subunit is responsible for activation of adenylate cyclase located on the basolateral cellular membrane.
What are the different types of lipid rafts known?
Lipid rafts are highly dynamic, detergent resistant, and enriched with both cholesterol and glycosphingolipids. The two main types are flotillin-rich planar lipid rafts and caveolin-rich caveolae.
Which lipids are enriched in lipid rafts?
Lipid rafts are considered Lo, they are enriched with sterols such as cholesterol and sphingolipids such as sphingomyelin and glycosphingolipids, and they are associated with specific proteins, so-called raft proteins (Fig. 1A).
What are lipid rafts and their function?
Lipid rafts are dynamic assemblies of proteins and lipids that float freely within the liquid-disordered bilayer of cellular membranes but can also cluster to form larger, ordered platforms. Rafts are receiving increasing attention as devices that regulate membrane function in eukaryotic cells.
What is the function of the A subunit in Vibrio toxin?
Subunit B binds while subunit A activates the G protein which activates adenylate cyclase.
Why does cholera toxin target intestinal epithelial cells?
The cholera toxin affects the epithelial cells in the intestine by interfering with the cells signalling pathway, the toxin causes overactivation of the signalling pathway that controls the activity of chloride channel proteins.
How does cholera affect the cell membrane?
Once cholera toxin binds to cell surface receptors, the A Protomer can enter the cell and bind with and activate its target effector: adenylate cyclase. Increasing adenylate cyclase activity will increase cellular levels of cAMP, increasing the activity of ion pumps that remove ions from the cell.
What are the major components of lipid raft?
Composition of lipid rafts Rafts are small platforms, composed of sphingolipids and cholesterol in the outer exoplasmic leaflet, connected to phospholipids and cholesterol in the inner cytoplasmic leaflet of the lipid bilayer. These assemblies are fluid but more ordered and tightly packed than the surrounding bilayer.
What are the main characteristics of lipid rafts?
Lipid rafts are subdomains of the plasma membrane that contain high concentrations of cholesterol and glycosphingolipids. They exist as distinct liquid-ordered regions of the membrane that are resistant to extraction with nonionic detergents.
How do lipid rafts affect membrane fluidity?
Lipid rafts influence membrane fluidity and membrane protein trafficking, thereby regulating neurotransmission and receptor trafficking. Lipid rafts are more ordered and tightly packed than the surrounding bilayer, but float freely within the membrane bilayer.
What does cholera toxin do to cells?
Abstract. Cholera diarrhoea is due to the action of a toxin that acts on all animal cells by stimulating the enzyme adenylate cyclase, which catalyses the production oc cyclic AMP from ATP.
How does cholera toxin enter the cell?
How does cholera toxin enter epithelial cells?
Binding and Entry via the PM. Cholera toxin begins its intracellular journey by binding to the ganglioside GM1 located on the outer leaflet of apical membranes of intestinal epithelial cells. GM1 is the vehicle that transports the toxin all the way backwards in the secretory pathway from PM to ER.