Posted: February 1st, 2023
The process of cell communication is not same in all cases. There exist at least four major types of cell communication namely autocrine signaling, paracrine signaling, endocrine signaling, and synaptic signaling. The mode of cell communication in these types of signaling pathways is explained below:
Autocrine signaling: It is the type of signaling where the signals or messages produced by a particular cell has effects on the same cell that produced the signal. The signals produced by them are known as local mediators. In this type of signaling, both the sender cell and target cell are same. This type of signaling is common in many biological processes, some of which are listed below:
In cancer cells, autocrine signaling is responsible for metastasis.
Autocrine signaling is seen in the cytokine interleukin-1 present in the monocytes. In response to specific external stimuli like activated macrophages, interleukin 1 is produced, which binds to the sender cell itself to bring about a suitable cell response like inflammation.
Proliferation of T lymphocytes, which are essential immune cells of the adaptive immunity.
Paracrine signaling: Paracrine signaling is the common communication that occurs between neighboring cells. In this type of signaling, the chemical message or the ligand sent by the sender cell travels over a short distance and binds to suitable receptors of another cell, which is present in the vicinity. This enables local coordination of different activities among the cells. The following are the few examples of paracrine signaling:
Paracrine signaling plays a key role during development process as paracrine signaling signals the group of neighboring cell about what cellular identity those cells should take on.
Paracrine signaling brings about transmission of messages between a neuron and muscle cell.
Clotting factors work by paracrine mode of signaling to bring about blood coagulation.
Endocrine signaling: Endocrine signaling occurs when chemical messengers have to travel long distances to induce specific metabolic reactions. In most cases, endocrine signaling system uses the circulatory system or the blood as the distributing network of the specific signals to their target cells. Specialized cells secrete signals and release them, directly into the blood stream and the blood carries these signals and delivers them into the target cells. Hormones are the chief chemical messengers, which are examples of endocrine signaling. In higher animals, special glands called endocrine glands release hormones as chemical messengers into the blood directly. The blood carries these hormones to the target cell or target site to carry out specific function. For example, the anterior pituitary secretes a hormone called thyroid stimulating hormone, which is carried by the blood to the target site, the thyroid gland.
Synaptic signaling: Synaptic signaling is a unique paracrine signal occurring in synapses. Synapses refer to the typical junction between two neurons and synapse is the region where signal transmission occurs. Whenever a neuron fires, the electrical impulses move rapidly down the fiber-like axons and reach the synapse. This induces the release of neurotransmitter from the synapse, which cross the small gap between neurons. After reaching the target cell, the neurotransmitter binds to suitable receptors and bring about appropriate reactions like opening the ion channels or altering the electrical potential across the membrane.
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