In multicellular organisms, the process of sending and receiving information between cells or within cells with high precision and efficiency, and causing rapid cellular physiological responses through amplification mechanisms.

Classification

A process in which cells respond to external stimuli or signals and transmit extracellular information to intracellular effector molecules through a series of orderly reactions involving the interaction of multiple molecules within the cell.

Soluble signals (transmitted between cells as free molecules)

Membrane-bound signaling molecules (requires cell-to-cell contact to transmit signals)

Receptors are usually special proteins on the cell membrane or within cells that can specifically recognize and bind to biologically active molecules, causing biological effects. Individual glycolipids also have receptor functions. Molecules that can specifically bind to receptors are called ligands, and soluble and membrane-bound signaling molecules are common ligands.

Classification

Receptors bind ligands and transduce signals

Common characteristics of receptor-ligand interactions

The process of ordered chemical changes formed by a specific set of signal transduction molecules and resulting in changes in cell behavior is called a signal transduction pathway

Signal transduction molecules in one pathway can interact with signal transduction molecules in other pathways. There are extensive cross-linking interactions between different signal transduction pathways, forming a complex signal transduction network.

small molecule second messenger

enzyme

regulatory protein

①Change the conformation of downstream signal transduction molecules

②Change the intracellular localization of signal transduction molecules

③Formation or depolymerization of signal transduction molecule complexes

④Change the intracellular concentration or distribution of small molecule messengers, etc.

After binding to the receptor, the ligand does not enter the cell, but can indirectly activate other small molecules or ions in the cell that can diffuse and regulate the activity of signal transduction proteins. These molecules that transmit signals within the cell are called second messengers. , also known as intracellular small molecule messenger.

Similar molecular characteristics of second messenger signals

cyclic nucleotides

Lipids, calcium ions, NO and other small molecules

Protein kinases and protein phosphatases regulate signaling

The GTP/GDP binding state of G protein determines signal transmission

Adapter proteins and scaffold proteins connect signal transduction networks

Abnormal receptor activation and inactivation

Abnormal activation and deactivation of signal transduction molecules

Cells acquire abnormal functions or phenotypes

loss of normal cell function