Cell signaling

1. Cell signaling Haleemashahin D.H Dpt of pharmacology

2. Cell to Cell Communication: • Communication between cells requires: • ligand: the signaling molecule • receptor protein: the molecule to which the receptor binds • may be on the plasma membrane orwithinthe cell • Cell signalingis part of a complex system of communication that governs basiccellular activities and coordinates cell actions. • The ability of cells to perceive and correctly respond to their microenvironment is the basis of development, tissue repair, and immunity as well as normal tissue homeostasis

3. Cells must be ready to respond to essential signals in their environment. These Cells must be ready to respond to essential signals in their environment. • These are often chemicals in the extracellular fluid (ECF) from:areoften chemicals in the extracellular fluid (Ecf)

4.  In most cases, a chain of reactions transmits signals from the cell surface to a variety of intracellular targets process called intracellular signal transduction. • The targets of such signaling pathways frequently include transcription factors that function to regulate gene expression. Intracellular signaling pathways thus connect the cell surface to the nucleus

5. Cell Communication: • There are five basic mechanisms for cellular communication: 1. Direct contact signaling 2. Paracrine signaling 3. Autocrine signaling 4. Endocrine signaling 5. Synaptic signaling

6. Paracrinesignaling • Paracrinesignaling is a form of cell-to-cell communication in which a cell produces a signal to induce changes in nearby cells, altering the behavior of those cells. • In paracrine signaling, the signaling molecules released by a cell only affect target cells in close proximity to it.The conduction of an electric impulse from one nerve cell to another or from a nerve cell to a muscle cell (inducing or inhibiting muscle contraction) occurs via paracrine signaling.

8. Autocrine signaling • Cells respond to substances that they themselves release. Many growth factors act in this fashion, and cultured cells often secrete growth factors that stimulate their own growth and proliferation. • This type of signaling is particularly common in tumor cells, many of which overproduce and release growth factors that stimulate inappropriate, unregulated proliferation of themselves as well as adjacent non tumorcells; this process may lead to formation of tumor mass.

10. Synaptic signaling is similar to paracrine signaling but there is a special structure called the synapse between the cell originating and the cell receiving the signal. • Synaptic signaling only occurs between cells with the synapse; for example between a neuron and the muscle that is controlled by neural activity.

11. Contact dependant a type of intracellular communication where by a signal molecule remains bound to the signalling cell surface, rather than being released inoexracellular space. • A membrane ligand(protein,oligosaccharidelipid )and a membrane protein of two adjacent cells interact. • A communicating junction links the intracellular compartments of two adjacent cells, allowing transit of relatively small molecules. • An extracellular matrix glycoprotein and a membrane protein interact.

12. Endocrine signaling • In endocrine signaling, signaling molecules, called hormones, act on target cells distant from their site of synthesis by cells of endocrine organs. • In animals, an endocrine hormone usually is carried by the blood from its site of release to its target.

13. Four forms of intercellular signaling Extracellular signal molecules can act over either short or long distances

15. The cell targeted by a particular chemicalsignalhas a receptor protein on or in thetargetcell that recognizes the signal molecule. Recognition occurs when the signal binds to a specific site on the receptor that is the complementary in shape to the signal. Ligand binding causes the receptor protein to undergo a change in shape that may activate the receptor so that it can interact with other molecules.

17. Cells communicate with each other through signaling molecules • Cells that produce the signaling molecule are referred to as signaling cells • Cells that receive the signal are target cells Hello! signaling cell target cell s

18. Signaling molecules could be proteins, small peptides, amino acids, nucleotides, steroids, retinoids, fatty acid derivatives, nitric oxide, carbon monoxide • The signaling molecule could either be secreted from the signaling cell or it could stay tightly bound to the cell surface of the signaling cell.

19. Extracellular signal molecules bind to specific receptors Regardless of the nature of the signal, the target cell responds by means of a receptor protein, which specifically binds the signal molecule and initiates a response