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[[File:Cell_signalling.png|Cell signalling|thumb]] [[File:_Autocrine_and_Paracrine.png|Autocrine and Paracrine|thumb|left]] [[File:Forms_of_Cell_Signaling.png|Forms of Cell Signaling|thumb|left]] [[File:Ligand-receptor_interaction.png|Ligand-receptor interaction|thumb]] [[Image:AMPA_receptor.png|AMPA receptor|thumb]] '''Cell signaling''' is a complex system of communication that governs basic cellular 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. Errors in signaling interactions and cellular information processing are responsible for diseases such as cancer, autoimmunity, and diabetes. By understanding cell signaling, scientists are able to develop better treatments for these diseases.

==Overview==
Cell signaling involves the transmission of a signal from a [[receptor]] on the cell's surface to its interior, leading to a cellular response. This process is critical for cells to respond to their environment and to communicate with other cells. Signaling can occur through a variety of mechanisms, including chemical signals, mechanical signals, and electrical signals. The main stages of cell signaling are reception, transduction, and response.

===Reception===
Reception occurs when a signaling molecule binds to a receptor on the cell surface. This receptor is typically a protein that changes its shape or activity upon binding, initiating the signal transduction pathway. Examples of receptors include [[G protein-coupled receptors]] (GPCRs) and [[receptor tyrosine kinases]] (RTKs).

===Transduction===
Transduction refers to the process by which the signal is relayed inside the cell. This often involves a series of changes in a sequence of different molecules, known as a signaling cascade. These molecules are usually proteins, which undergo modifications such as phosphorylation. Key players in signal transduction include [[second messengers]], [[protein kinases]], and [[phosphatases]].

===Response===
The final stage of cell signaling is the response, where the signal leads to a specific cellular activity. This could involve altering the transcription of genes, changing the cell's metabolism, or directly affecting the cell's structure and mobility. The response is tailored to the specific signal and cell type, ensuring appropriate actions are taken.

==Types of Signaling==
Cell signaling can be classified into several types based on the distance between the signaling and target cells:

* '''Autocrine signaling''' occurs when a cell targets itself, releasing a signal that binds to receptors on its own surface.
* '''Paracrine signaling''' involves signals sent from a cell to nearby cells, affecting local cells in the vicinity.
* '''Endocrine signaling''' relies on hormones transported by the bloodstream to reach cells throughout the body.
* '''Juxtacrine signaling''' requires direct contact between the signaling and the target cell, often through cell junctions or membrane-bound ligands.

==Signaling Pathways==
Several key signaling pathways have been identified, each with specific roles in cell function and development. These include the [[Notch signaling pathway]], [[Wnt signaling pathway]], [[Hedgehog signaling pathway]], and [[MAPK/ERK pathway]]. These pathways control a wide range of processes, from cell fate determination to apoptosis (programmed cell death).

==Clinical Significance==
Abnormalities in cell signaling pathways are a common cause of diseases. For example, mutations in the components of the Notch signaling pathway can lead to cancer. Understanding these pathways allows for the development of targeted therapies, such as inhibitors of specific kinases in cancer treatment.

[[Category:Cell biology]]
[[Category:Signal transduction]]

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Cell signaling - Revision history

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