Editing Signal transduction (section)

{{Short description|Cascade of intracellular and molecular events for transmission/amplification of signals}}
{{About|signaling at the cellular level|systemic signal transduction|Transduction (physiology)}}
[[File:Signal transduction pathways.svg|thumb|481x481px|Simplified representation of major signal transduction pathways in mammals.]]
'''Signal transduction''' is the process by which a chemical or physical signal is transmitted through a cell as a [[biochemical cascade|series of molecular events]]. Proteins responsible for detecting stimuli are generally termed [[receptor (biology)|receptors]], although in some cases the term sensor is used.<ref>{{Cite book |title=Handbook of Cell Signaling |date=2010 |publisher=Academic Press |isbn=9780123741455 |editor-last=Bradshaw |editor-first=Ralph A. |edition=2nd |location=Amsterdam, Netherlands |editor-last2=Dennis |editor-first2=Edward A. |name-list-style=vanc}}</ref> The changes elicited by [[ligand (biochemistry)|ligand]] binding (or signal sensing) in a receptor give rise to a [[biochemical cascade]], which is a chain of biochemical events known as a [[Cell signaling#Signaling pathways|signaling pathway]].

When signaling pathways interact with one another they form networks, which allow cellular responses to be coordinated, often by combinatorial signaling events.<ref>{{Cite journal |vauthors=Papin JA, Hunter T, Palsson BO, Subramaniam S |date=February 2005 |title=Reconstruction of cellular signalling networks and analysis of their properties |journal=Nature Reviews. Molecular Cell Biology |volume=6 |issue=2 |pages=99–111 |doi=10.1038/nrm1570 |pmid=15654321 |s2cid=3065483}}</ref> At the molecular level, such responses include changes in the [[transcription (biology)|transcription]] or [[translation (biology)|translation]] of genes, and [[post-translational modification|post-translational]] and conformational changes in proteins, as well as changes in their location. These molecular events are the basic mechanisms controlling [[cell growth]], proliferation, [[metabolism]] and many other processes.<ref>{{Cite book |last=Krauss |first=Gerhard |url=https://archive.org/details/biochemistryofsi00krau/page/15/mode/2up |title=Biochemistry of Signal Transduction and Regulation |date=2008 |publisher=Wiley-VCH |isbn=978-3527313976 |pages=15 |name-list-style=vanc}}</ref> In multicellular organisms, signal transduction pathways regulate [[Cellular communication (biology)|cell communication]] in a wide variety of ways.

Each component (or node) of a signaling pathway is classified according to the role it plays with respect to the initial stimulus. [[Ligand (biochemistry)|Ligands]] are termed ''first messengers'', while receptors are the ''signal transducers'', which then activate ''primary effectors''. Such effectors are typically proteins and are often linked to [[second messenger]]s, which can activate ''secondary effectors'', and so on. Depending on the efficiency of the nodes, a signal can be amplified (a concept known as signal gain), so that one signaling molecule can generate a response involving hundreds to millions of molecules.<ref name="Campbell">{{Cite book |last=Reece |first=Jane |url=https://archive.org/details/biologyc00camp |title=Biology |last2=Campbell |first2=Neil |publisher=Benjamin Cummings |year=2002 |isbn=978-0-8053-6624-2 |location=San Francisco |name-list-style=vanc}}</ref> As with other signals, the transduction of biological signals is characterised by delay, noise, signal feedback and feedforward and interference, which can range from negligible to pathological.<ref>{{Cite journal |vauthors=Kolch W, Halasz M, Granovskaya M, Kholodenko BN |date=September 2015 |title=The dynamic control of signal transduction networks in cancer cells |journal=Nature Reviews. Cancer |volume=15 |issue=9 |pages=515–27 |doi=10.1038/nrc3983 |pmid=26289315 |s2cid=35252401}}</ref> With the advent of [[computational biology]], the [[systems biology|analysis]] of signaling pathways and networks has become an essential tool to understand cellular functions and [[disease]], including signaling rewiring mechanisms underlying responses to acquired drug resistance.<ref>Bago R, Sommer E, Castel P, Crafter C, Bailey FP, Shpiro N, Baselga J, Cross D, Eyers PA, Alessi DR (2016) The hVps34-SGK3 pathway alleviates sustained PI3K/Akt inhibition by stimulating mTORC1 and tumour growth. EMBO Journal 35:1902-22</ref>