Cell Signaling and its types

Cell Signaling (Cell Communication)

Definition: Cell signaling is the ability of a cell to receive, process, and transmit signals with its environment and with itself.

It is the basic property of all cells and is essential for survival, growth and development of an organism.

Cells primarily communicates through chemical signals or called ligands (signaling molecules).

Ligands are secreted by the sending cells and the target cell has a receptor specific for this ligand. Binding of ligand to the receptor causes some conformational changes that further activate some other proteins inside the cell and finally causing a cellular response.

4 types of Cell signaling

4 Types of Cell Signaling
           Image credit:https://courses.lumenlearning.com/suny-ap2/chapter/hormones/ (CC BY 4.0)

Based on distance travelled by the ligands or signaling molecule

1.      Autocrine Signaling (self-communication): Cells respond to the signal produced by themselves.

Eg: T cell proliferation and differentiation by cytokines secreted by T cells itself

Secretion of IL1 by macrophages activates macrophages itself.

2.      Paracrine (para: nearby) (short distance signaling): Signaling molecules produced by the sender cell affects neighboring target cells

Eg: Synaptic signaling (conduction of an electrical signal from one nerve cell to another at a synapse using neurotransmitter as signaling molecules. Neurotransmitter released from the presynaptic cell binds to the receptor on the post synaptic cell causing cellular responses like opening of ion channel, change in membrane potential across the membrane etc.)

3.      Endocrine Signaling (Long distance signaling): Signaling molecules (hormones) are secreted by endocrine cells carried through the blood stream to distant target cells

Eg: Signaling of hormones; Estrogen hormones produced by ovary stimulates development and maintenance of female reproductive system and associated secondary sex characteristics.

4.      Direct cell to cell signaling: through gap junctions in animals and plasmodesmata in plants. Communication junctions allows ions and small molecules to pass through to the next cell ensuring direct intercellular communication. Direct cell to cell signaling is crucial in early embryonic development and maintenance of tissues.

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