In biology, an effector is a general term that can refer to several types of molecules or cells depending on the context:
Small molecule effectors
A small molecule that selectively binds to a protein to regulate its biological activity can be called an effector. In this manner, effector molecules act as ligands that can increase or decrease enzyme activity, gene expression, influence cell signaling, or other protein functions. An example of such an effector is oxygen, which is an allosteric effector of hemoglobin - oxygen binding to one of the four hemoglobin subunits greatly increases the affinity of the rest of the subunits to oxygen.[1] Certain drug molecules also fall into this category - for example the antibiotic rifampicin used in the treatment of tuberculosis binds the initiation σ factor subunit of the bacterial RNA polymerase, preventing the transcription of bacterial genes.[2]
The term can also be used to describe small molecules that can directly bind to and regulate the expression of mRNAs.[3] One example for such an effector is guanine, which can be recognised by specific sequences (known as riboswitches) found on mRNAs, and its binding to those sequences prevents the translation of the mRNA into a protein.[4] See also: purine riboswitch.
Protein effectors
An effector can also be used to refer to a protein that is involved in cellular signal transduction cascades. Such an example are RAS effector proteins, which are all able to bind RAS.GTP, but trigger different cell pathways upon doing so - such as the Ras-Raf-MEK-ERK pathway, the PI3K pathway or several others.[5]
An effector hormone is a hormone that acts on a particular tissue - an example of such a hormone is thyroxine (T4), which regulates metabolism in many tissues throughout the body.[6]
Antibody Effectors are effectors involved with the production and secretion of molecules involved in pathogen defense, such as Immunoglobulin. Many antibodies then act as effector molecules for the immune system of the organism.[7]
Bacterial effector proteins are proteins injected by (usually pathogenic) bacterial cells into the cells of their host. The injected proteins serve different functions dependent on the bacteria of origin, but typically serve the purpose of inhibiting the host cells immune response.[8] An example of these are the Transcription activator-like effector (TALE) proteins secreted by bacteria from the genus Xanthomonas.[9]
Fungal effectors are secreted by pathogenic or beneficial fungi into and around host cells by invasive hyphae to disable defense components or facilitate colonization. Protein secretion systems in fungi involve the Spitzenkörper.[10]
RNA effectors
Certain plant pathogens, such as Botrytis cinerea, secrete small RNAs (sRNAs) into the host cells and downregulate plant proteins involved in the immune response by RNA interference.[11]
Effector cells
In immunology, effector cells are cells of either the innate or the adaptive immune system that mediate the immune response.[12]
Effector neurons can be used to refer to population of neurons in the nervous system, which are responsible for a certain brain function. An example are the neurons in the mesopontine tegmental anesthesia area (MPTA) of the brainstem, which have been mapped as the region of the brain that is responsive to anaesthetics in a rodent model.[13]
^Takayanagi, Masayoshi; Kurisaki, Ikuo; Nagaoka, Masataka (2014-04-08). "Non-site-specific allosteric effect of oxygen on human hemoglobin under high oxygen partial pressure". Scientific Reports. 4 (1): 4601. Bibcode:2014NatSR...4E4601T. doi:10.1038/srep04601. ISSN 2045-2322. PMC 3978498. PMID 24710521.
^Artsimovitch, Irina; Vassylyeva, Marina N.; Svetlov, Dmitri; Svetlov, Vladimir; Perederina, Anna; Igarashi, Noriyuki; Matsugaki, Naohiro; Wakatsuki, Soichi; Tahirov, Tahir H.; Vassylyev, Dmitry G. (2005-08-12). "Allosteric Modulation of the RNA Polymerase Catalytic Reaction Is an Essential Component of Transcription Control by Rifamycins". Cell. 122 (3): 351–363. doi:10.1016/j.cell.2005.07.014. ISSN 0092-8674. PMID 16096056. S2CID 8237649.
^Garst, A. D.; Edwards, A. L.; Batey, R. T. (2011-06-01). "Riboswitches: Structures and Mechanisms". Cold Spring Harbor Perspectives in Biology. 3 (6): a003533. doi:10.1101/cshperspect.a003533. ISSN 1943-0264. PMC 3098680. PMID 20943759.
^Mulhbacher, Jérôme; Lafontaine, Daniel A. (August 2007). "Ligand recognition determinants of guanine riboswitches". Nucleic Acids Research. 35 (16): 5568–5580. doi:10.1093/nar/gkm572. ISSN 1362-4962. PMC 2018637. PMID 17704135.
^Kiel, Christina; Matallanas, David; Kolch, Walter (2021). "The Ins and Outs of RAS Effector Complexes". Biomolecules. 11 (2): 236. doi:10.3390/biom11020236. PMC 7915224. PMID 33562401.
^Tendler, Avichai; Bar, Alon; Mendelsohn-Cohen, Netta; Karin, Omer; Kohanim, Yael Korem; Maimon, Lior; Milo, Tomer; Raz, Moriya; Mayo, Avi; Tana, Amos; Uri, Alon (2021-09-15). "Hormone seasonality in medical records suggests circannual endocrine circuits". Yearbook of Paediatric Endocrinology. 118 (7). doi:10.1530/ey.18.15.12. ISSN 1662-4009. PMC 7896322. PMID 33531344.
^Oostindie SC, Lazar GA, Schuurman J, Parren PW (October 2022). "Avidity in antibody effector functions and biotherapeutic drug design". Nature Reviews. Drug Discovery. 21 (10): 715–735. doi:10.1038/s41573-022-00501-8. PMC 9255845. PMID 35790857.
^Wagner S, Grin I, Malmsheimer S, Singh N, Torres-Vargas CE, Westerhausen S (October 2018). "Bacterial type III secretion systems: a complex device for the delivery of bacterial effector proteins into eukaryotic host cells". FEMS Microbiology Letters. 365 (19). doi:10.1093/femsle/fny201. PMC 6140923. PMID 30107569.
^Strauß, Tina; van Poecke, Remco M. P.; Strauß, Annett; Römer, Patrick; Minsavage, Gerald V.; Singh, Sylvia; Wolf, Christina; Strauß, Axel; Kim, Seungill; Lee, Hyun-Ah; Yeom, Seon-In; Parniske, Martin; Stall, Robert E.; Jones, Jeffrey B.; Choi, Doil (2012-11-20). "RNA-seq pinpoints a Xanthomonas TAL-effector activated resistance gene in a large-crop genome". Proceedings of the National Academy of Sciences. 109 (47): 19480–19485. Bibcode:2012PNAS..10919480S. doi:10.1073/pnas.1212415109. ISSN 0027-8424. PMC 3511116. PMID 23132937.
^Steinberg G (March 2007). "Hyphal growth: a tale of motors, lipids, and the Spitzenkörper". Eukaryotic Cell. 6 (3): 351–360. doi:10.1128/EC.00381-06. PMC 1828937. PMID 17259546.
^Wang, Ming; Weiberg, Arne; Jin, Hailing (April 2015). "Pathogen small RNAs: a new class of effectors for pathogen attacks: Pathogen small RNAs at attack". Molecular Plant Pathology. 16 (3): 219–223. doi:10.1111/mpp.12233. PMC 6638317. PMID 25764211.
^Arnone, Baron; Zhao, Xiaoqi; Zou, Zhipeng; Qin, Gangjian; Cheng, Min (2015-01-01), Tang, Yaoliang; Dawn, Buddhadeb (eds.), "Chapter 11 - Diagnostic and Prognostic Applications of MicroRNA-Abundant Circulating Exosomes", Mesenchymal Stem Cell Derived Exosomes, Boston: Academic Press, pp. 223–256, doi:10.1016/b978-0-12-800164-6.00011-3, ISBN 978-0-12-800164-6, retrieved 2023-01-18
^Baron, Mark; Vaso, Kristina; Avigdor, Tamir; Charit, Yelena; Minert, Anne; Devor, Marshall (2022-11-01). "Anesthetic loss of consciousness induced by chemogenetic excitation of mesopontine effector neurons". Experimental Neurology. 357: 114169. doi:10.1016/j.expneurol.2022.114169. ISSN 0014-4886. PMID 35817130. S2CID 250361680.
