What are the Major Signalling Pathways?

Signalling pathways are often categorised into a few major groups and their classification depends on the way they are activated, in the first place. It is important for the cell to communicate with its own environment and this is done so that suitable responses can be made. It is possible for external signal to enter a cell through major pathways – hydrophobic molecules, Enzymes, G-protein-coupled receptors and Ion channels. Let us know more about them.

Hydrophobic Molecules Signalling: It is through the lipid bilayers that hydrophobic molecules pass through; they usually move in and move out. Nitric oxide, steroids and arachidonic acid play a vital role in cell signalling.

Ion Channels Signalling: Ion channels allow ions to pass through since they are the membrane proteins; when it comes to selectivity of ions, they can be classified as sodium channels, calcium channels and potassium channels. When considered ‘gating’ (term used for defining the way channels open up), they can also be classified as ligand-gated channels and voltage-gated channels.

G-Protein-Coupled Receptors Signalling: Three G protein subunits are bound together and this is done before the G-protein-coupled receptor binding. It is the agonist binding that leads to an interaction between G protein and G-protein-coupled receptor and ultimately it is this interaction that leads into the disassociation between the diverse subunits of G protein; separated subunits may then establish an interaction with effectors.

Cell Surface Enzymes Signalling: Receptor serine/threonine kinases and Receptor tyrosine kinases are the receptors of the cell surface. Function of Receptor tyrosine phosphatase is to catalyse dephosphorylation of the residue of tyrosine. On the other hand, Receptor guanylyl cyclase will catalyse cGMP synthesis.

In a lot of cases, signal propagates right within the cell and most of the time it reaches nuclear DNA so that proteins can be expressed. These are the major signalling pathways that contribute to making cell signalling an interesting area of study.

Share |