Editing Nutrient sensing

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'''Nutrient sensing''' is a [[cell (biology)|cell]]'s ability to recognize and respond to fuel substrates such as [[glucose]]. Each type of fuel used by the cell requires an alternate pathway of utilization and [[accessory molecule]]s such as [[enzyme]]s and [[Cofactor (biochemistry)|cofactor]]s. In order to conserve resources a cell will only produce molecules that it needs at the time.  The level and type of fuel that is available to a cell will determine the type of [[enzymes]] it needs to express from its [[genome]] for utilization. [[Receptor (biochemistry)|Receptors]] on the [[cell membrane|cell membrane's]] surface designed to be activated in the presence of specific fuel molecules communicate to the [[cell nucleus]] via a means of [[cascading interactions]]. [[Nutrient receptor]]s are receptors that are primarily designed to perform the function of nutrient sensing, whereas other receptors (e.g. [[insulin receptor]]s, [[leptin receptor]]s) are extensively multifunctional and perform many functions besides nutrient sensing.<ref>{{Cite journal |last=A. Nguyen |first=C. |last2=Akiba |first2=Y. |last3=D. Kaunitz |first3=J. |date=2012-01-01 |title=Recent Advances in Gut Nutrient Chemosensing |url=https://www.ingentaconnect.com/content/ben/cmc/2012/00000019/00000001/art00005 |journal=Current Medicinal Chemistry |volume=19 |issue=1 |pages=28–34 |doi=10.2174/092986712803414033|pmc=4845632 }}</ref> In this way the cell is aware of the available nutrients and is able to produce only the molecules specific to that nutrient type.

==Nutrient sensing in mammalian cells==

A rapid and efficient response to disturbances in nutrient levels is crucial for the survival of organisms from bacteria to humans. Cells have therefore evolved a host of molecular pathways that can sense nutrient concentrations and quickly regulate gene expression and protein modification to respond to any changes.<ref>Zagorski, Nick. "Nutrient Sensing, Signaling, & Regulation." Journal of Biological Chemistry. (2010): n. page. Web. 9 Apr. 2013. http://www.jbc.org/site/meeting2010/nutrient</ref>

Cell growth is regulated by coordination of both extracellular nutrients and intracellular metabolite concentrations. [[AMP-activated protein kinase|AMP-activated kinase (AMPK)]] and [[MTORC1|mammalian target of rapamycin complex 1]] serve as key molecules that sense cellular energy and nutrients levels, respectively.
*The interplay among nutrients, metabolites, gene expression, and protein modification are involved in the coordination of cell growth with extracellular and intracellular conditions.<ref>Molecular Cell, Volume 49, Issue 3, 379-387, 7 February 2013</ref>

Living cells use [[Adenosine triphosphate|ATP]] as the most important direct energy source. Hydrolysis of ATP to [[Adenosine diphosphate|ADP]] and [[phosphate]] (or [[Adenosine monophosphate|AMP]] and [[pyrophosphate]]) provides energy for most biological processes. The ratio of ATP to ADP and AMP is a barometer of cellular energy status and is therefore tightly monitored by the cell. In eukaryotic cells, AMPK serves as a key cellular energy sensor and a master regulator of metabolism to maintain energy homeostasis.<ref>{{cite journal|author=Yuan, Hai-Xin|title=Nutrient Sensing, Metabolism, and Cell Growth Control|journal= Molecular Cell|year=2013|volume=49|issue=3|pages=379–387|doi=10.1016/j.molcel.2013.01.019|pmid=23395268|pmc=3587157|access-date=2 April 2013|url=http://www.stanford.edu/class/cbio101/coursework/yuan2013.pdf}}</ref>

==Nutrient sensing and epigenetics==

Nutrient sensing and signaling is a key regulator of [[Epigenetics|epigenetic]] machinery in cancer. During glucose shortage, the energy sensor AMPK activates arginine methyltransferase [[CARM1]] and mediates [[histone H3]] hypermethylation ([[H3R17me2]]), leading to enhanced [[autophagy]]. In addition, [[Protein O-GlcNAc transferase|''O''-GlcNAc transferase (OGT)]] signals glucose availability to TET3 and inhibits TET3 by both decreasing its dioxygenase activity and promoting its nuclear export. OGT is also known to directly modify histones with [[O-GlcNAc|''O''-GlcNAc]]. These observations strongly suggest that nutrient signaling directly targets epigenetic enzymes to control epigenetic modifications.<ref>{{cite journal | vauthors = Wang YP, Lei QY | title = Metabolic recoding of epigenetics in cancer | journal = Cancer Commun (Lond) | volume = 38 | issue = 1 | pages = 1–8 | pmid = 29784032 | pmc = 5993135 | doi = 10.1186/s40880-018-0302-3 | year = 2018 | doi-access = free }}</ref>

==Regulation of tissue growth==

Nutrient sensing is a key regulator of tissue growth. The main mediator of cellular nutrient sensing is the protein kinase [[MTOR|TOR (target of rapamycin)]]. TOR receives information from levels of cellular [[amino acid]]s and energy, and it regulates the activity of processes involved in cell growth, such as protein synthesis and autophagy. Insulin-like signaling is the main mechanism of systemic nutrient sensing and mediates its growth-regulatory functions largely through the protein kinase pathway. Other nutrition-regulated hormonal mechanisms contribute to growth control of modulating the activity of insulin-like signaling.<ref>{{cite journal |pmid=19694515 | doi=10.1146/annurev-genet-102108-134815 | volume=43 | title=Regulation of tissue growth through nutrient sensing | year=2009 | journal=Annu. Rev. Genet. | pages=389–410 | last1 = Hietakangas | first1 = V | last2 = Cohen | first2 = SM}}</ref>

==Nutrient sensing in plants==

Higher plants require a number of essential nutrient elements for completing their life cycles. Mineral nutrients are mainly acquired by roots from the [[rhizosphere]] and are subsequently distributed to shoots. To overcome with nutrient limitations, plants have evolved a set of elaborate responses consisting of sensing mechanisms and signaling processes to perceive and adapt to external nutrient availability.<ref name=Cui2012 />

Plants obtain most necessary nutrients by taking them up from the soil into their roots. Although plants cannot move to a new environment when nutrient availability is less than favorable, they can modify their development to favor root colonization of soil areas where nutrients are abundant. Therefore, plants perceive the availability of external nutrients, like nitrogen, and couple this nutrient sensing to an appropriate adaptive response.

===Types of nutrients in plants===

Potassium (K<sup>+</sup>) and phosphorus (P<sup>+</sup>) are important macronutrients for crops but are often deficient in the field. Very little is known about how plants sense fluctuations in concentrations of K<sup>+</sup> and P<sup>+</sup>, and how such sensing is integrated at the organismic level into physiological and metabolic adaptations.<ref>{{Cite web |last=Press |first=Cell |title=Getting to the root of nutrient sensing |url=https://phys.org/news/2010-06-root-nutrient.html |access-date=2023-12-30 |website=phys.org |language=en}}</ref><ref>{{Citation |last=Amtmann |first=Anna |title=Nutrient Sensing and Signalling in Plants: Potassium and Phosphorus |date=2005-01-01 |url=https://www.sciencedirect.com/science/article/pii/S0065229605430050 |work=Advances in Botanical Research |volume=43 |pages=209–257 |access-date=2023-12-30 |series=Incorporating Advances in Plant Pathology |publisher=Academic Press |last2=Hammond |first2=John P. |last3=Armengaud |first3=Patrick |last4=White |first4=Philip J.}}</ref> Smaller amounts of other [[Nutrient|micronutrients]] are also important for the growth of the crop. All of these nutrients are equally important for the growth of the plant and lack of one nutrient can result in poor growth of the plant as well as becoming more vulnerable to diseases or can lead to death.<ref name=":02">{{Cite web |date=2002 |title=What Nutrients do Plants need? |url=http://www.agroservicesinternational.com/Education/Fert1.html |url-status=dead |archive-url=https://web.archive.org/web/20210427071459/https://www.agroservicesinternational.com/Education/Fert1.html |archive-date=2021-04-27 |website=Agro Services International}}</ref> These nutrients along with {{CO2}} and energy from the sun aids in the development of the plant.<ref name=":12">{{Cite book |url=http://www.mhhe.com/biosci/genbio/raven6b/graphics/raven06b/other/raven06_39.pdf |archive-url=https://web.archive.org/web/20041122052625/http://www.mhhe.com/biosci/genbio/raven6b/graphics/raven06b/other/raven06_39.pdf |url-status=dead |archive-date=22 November 2004 |title=Higher Education Support {{!}} McGraw Hill Higher Education}}</ref>

===Nitrogen sensing===
As one of the most vital nutrients for the development and growth of all plants, [[nitrogen]] sensing and the signalling response are vital for plants to live.<ref>{{cite journal|last1=Kruok|first1=Gabriel|last2=Benoît|first2=Lacombe|last3=Agnieszka|first3=Bielach|last4=Perrine-Walker|first4=Francine|last5=Malinska|first5=Katerina|last6=Mounier|first6=Emmanuelle|last7=Hoyerova|first7=Klara|last8=Tillard|first8=Pascal|last9=Leon|first9=Sarah|last10=Ljung|first10=Karin|last11=Zazimalova|first11=Eva|title=Nitrate-Regulated Auxin Transport by NRT1.1 Defines a Mechanism for Nutrient Sensing in Plants|journal=Developmental Cell|date=June 15, 2010|volume=18|issue=6|pages=927–937|doi=10.1016/j.devcel.2010.05.008|pmid=20627075|doi-access=free}}</ref> Plants absorb nitrogen through the soil in the form of either [[nitrate]] or [[ammonia]].<ref name=":0">{{cite journal|last1=Ho|first1=Cheng-Hsun|last2=Tsay|first2=Yi-Fang|title=Nitrate, ammonium, and potassium sensing and signaling|journal=Current Opinion in Plant Biology|date=October 2010|volume=13|issue=5|pages=604–610|doi=10.1016/j.pbi.2010.08.005|pmid=20833581|doi-access=free}}</ref> In soil with low oxygen levels, ammonia is the primary nitrogen source, but toxicity is carefully controlled for with the transcription of ammonium transporters (AMTs).<ref name=":0" /> This metabolite and others including glutamate and glutamine have been shown to act as a signal of low nitrogen through regulation of nitrogen transporter gene transcription.<ref name=":1">{{Cite journal|last1=Coruzzi|first1=Gloria M|last2=Zhou|first2=Li|date=2001-06-01|title=Carbon and nitrogen sensing and signaling in plants: emerging 'matrix effects'|journal=Current Opinion in Plant Biology|volume=4|issue=3|pages=247–253|doi=10.1016/s1369-5266(00)00168-0|pmid=11312136}}</ref> NRT1.1, also known as CHL1, is the nitrate transceptor (transporter and receptor) found on the plasma membrane of plants.<ref name=":0" /> This is both a high and low affinity transceptor that senses varying concentrations of nitrate depending on its T101 residue phosphorylation.<ref name=":0" /> It has been shown that nitrate can also act as just a signal for plants, since [[mutants]] unable to metabolize are still able to sense the [[ion]].<ref name=":1" /> For example, many plants show the increase of nitrate-regulated genes in low nitrate conditions and consistent [[mRNA]] transcription of such genes in soil high in nitrate.<ref name=":1" /> This demonstrates the ability to sense nitrate soil concentrations without [[metabolic]] products of nitrate and still exhibit downstream genetic effects.<ref name=":1" />

=== Potassium Sensing ===
[[Potassium]] (K+), one of the essential [[Nutrient|macronutrients]] is found in plant soil. K+ is the most abundant cation and it is very limited in plant soil. Plants absorb K+ from the soil through channels that are found at the [[Plasma membrane Ca2+ ATPase|plasma membrane]] of root cells. Potassium is not assimilated into organic matter like other nutrients such as [[nitrate]] and [[ammonium]] but serves as a major osmoticum.<ref name=Cui2012>{{cite journal|title=Nutrient Sensing in Plants | doi=10.1093/mp/sss107 |pmid=23024206 | volume=5|issue=6 |journal=Molecular Plant|pages=1167–1169 | last1 = Cui | first1 = Xiaofeng|year=2012 |doi-access=free }}</ref>

==Brain and gut regulation of food intake==

Maintaining a careful balance between stored energy and caloric intake is important to ensure that the body has enough energy to maintain itself, grow, and engage in activity. When balanced improperly, obesity and its accompanying disorders can result.<ref>{{cite web |last=Dove |first=Alan |date=2009-04-09 |title=Nutrient Sensing: How the Brain and Gut Regulate Food Intake |url=https://www.nyas.org/ebriefings/nutrient-sensing/ |url-access=registration |work=Diabetes & Obesity Discussion Group |publisher=New York Academy of Sciences (NYAS)}}</ref>

==References==
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[[Category:Nutrition]]
[[Category:Receptors]]