Cell signaling
In biology, cell signaling (cell signalling in
British English), or cell-cell
communication, governs the basic
activities of cells and coordinates
Multiple-cell actions.[1] A signal is an entity that codes or conveys information.
As you know that the Biological processes are complex
Molecular interactions that involve many signals.As well as normal tissue homeostasis.Diseases such as cancer, autoimmunity, and diabetes are causes of errors in cell signaling.
[2][3][4] By understanding cell signaling, clinicians may treat Diseases
more effectively and, theoretically,
researchers may develop artificial
tissues.[5]
All cells receive and respond to signals
From their surroundings. This is
accomplished by a variety of signal
molecules that are secreted or expressed on the surface of one cell and bind to a
receptor expressed by the other cells,
thereby integrating and coordinating the
Function of the many individual cells that make up organisms. The response to specific
extracellular signal molecules is programmed by each cell
Signaling usually are of the
following steps:
1. Synthesis is occurred by the release of the signaling
molecule by the signaling cell;
2.The target transport of signal
cell;
3. Binding of the signal by a specific
Signaling agents could be physical agents like mechanical pressure, voltage, temperature, and light or chemical agents like peptides, steroids, terpenoids, etc. It may be food material or pathogenassociated patterns, or it may be oxygen
Or carbon dioxide levels or specially
Biosynthesized signaling molecules like
Hormones and ferromones
(Ektohormones). Signaling molecules vary greatly in their physio-chemical properties such as solubility (hydrophobic or hydrophilic). Some signaling molecules are gaseous, such as nitric oxide. Additionally, proteins on the surface of neighboring cells could also be signals.various biosynthetic pathways, and happens in specific time and place synthesis involves. Signal molecules may be released from the cell and sometimes they are not released at all, such as cellular localization signals and DNA damage signals.molecules that can be released through various ways like membrane-diffusion,exocytosis or cell damage. In some cases the signal molecules remain attached with
Cell-surface, a mode that helps in
Juxtacrine signaling (discussed below).
Sometimes signal molecules require activation, such as through proteolytic cleavage or covalent modifications.
The ultimate path of the signal may be intracellular or intercellular. The intercellular signaling is also called cellto-cell communication. It can be Based on nature of this path of signal molecule from source to target cell; the signaling pathways are classified into autocrine, juxtacrine, intracrine,paracrine and endocrine (discussed below)
Receptors play a key role in cell signaling.
Receptors help in recognising the signal molecule (ligand). However some receptor molecules respond to physical agents (voltage, light, etc).As you know that Receptor molecules are generally proteins. Receptors may be located at cell surface, or interior of the cell such as cytosol, the organelles and nucleus (especially the transcription
factors). Usually the cell surface
Receptors bind membrane-impermeable
Signal molecules, but sometimes they also
Interact with membrane permeable signalmolecules. A key step in signaling is
Removal and degradation of the signal
Molecule. Sometimes the receptor is also
Degraded. Neurotransmitter reuptake is a
Mechanism of signaling molecule removal
That is commonly seen in nervous system,
And is a target of some class of
Prescription psychiatric medications.
Binding with the ligand causes
conformational change in the receptor,
which leads to further transmission of
Signaling. Due to conformational change,
The receptor may either show an enzymic
activity (called enzymic receptor), or a ion
Channel opening or closing activity (called a channel receptor). Sometimes the
receptors themselves do not contain
Enzymatic or channel-like domains but
They are linked with an enzyme or transporter.
Some receptors (like the nuclear cytoplasmic super family) have a different
Mechanism. Once they bind with signal,
They change their DNA binding properties
And cellular localization to the nucleus.
Result of enzymatic activity of the
receptor usually leads to recruitment of
additional molecular changes, thus causing
A signal transduction "cascade". These
Intermediates often forms a second
Messenger system. Within the signal
Classification
Cell signaling can be classified as either
mechanical or biochemical based on the
Type of the signal. Mechanical signals are
the forces exerted on the cell and the
Forces produced by the cell. These forces
can both be sensed and responded to by
the cells.[13] Biochemical signals are
biochemical molecules such as proteins,
lipids, ions, and gases. These signals can
be categorized based on the distance
Between signaling and responder cells signaling within, between, and amongst.
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