Editing ABC transporter (section)

=== Eukaryotic ===

Although most eukaryotic ABC transporters are effluxers, some are not directly involved in transporting substrates. In the [[cystic fibrosis]] transmembrane regulator ([[Cystic fibrosis transmembrane conductance regulator|CFTR]]) and in the [[sulfonylurea]] receptor (SUR), ATP hydrolysis is associated with the regulation of opening and closing of ion channels carried by the ABC protein itself or other proteins.<ref name=goffeau/>

Human ABC transporters are involved in several diseases that arise from [[Polymorphism (biology)|polymorphisms]] in ABC genes and rarely due to complete loss of function of single ABC proteins.<ref name=pohl>{{cite journal | vauthors = Pohl A, Devaux PF, Herrmann A | title = Function of prokaryotic and eukaryotic ABC proteins in lipid transport | journal = Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids | volume = 1733 | issue = 1 | pages = 29–52 | date = Mar 2005 | pmid = 15749056 | doi = 10.1016/j.bbalip.2004.12.007 }}</ref> Such diseases include [[Mendelian]] diseases and complex genetic disorders such as cystic fibrosis, [[adrenoleukodystrophy]], [[Stargardt disease]], [[Tangier disease]], immune deficiencies, progressive familial intrahepatic [[cholestasis]], [[Dubin–Johnson syndrome]], [[Pseudoxanthoma elasticum]], persistent [[hyperinsulinemic hypoglycemia]] of infancy due to focal adenomatous [[hyperplasia]], X-linked [[sideroblastic anemia|sideroblastosis and anemia]], age-related [[macular degeneration]], familial hypoapoproteinemia, Retinitis pigmentosum, [[corneal dystrophy|cone rod dystrophy]], and others.<ref name=goffeau/> The human ABCB (MDR/TAP) family is responsible for [[multiple drug resistance]] (MDR) against a variety of structurally unrelated drugs. ABCB1 or MDR1 [[P-glycoprotein]] is also involved in other biological processes for which lipid transport is the main function. It is found to mediate the secretion of the steroid [[aldosterone]] by the adrenals, and its inhibition blocked the migration of [[Dendrite (non-neuronal)|dendritic]] immune cells,<ref name="pmid11502161">{{cite journal | vauthors = Randolph GJ | title = Dendritic cell migration to lymph nodes: cytokines, chemokines, and lipid mediators | journal = Seminars in Immunology | volume = 13 | issue = 5 | pages = 267–74 | year = 2001 | pmid = 11502161 | doi = 10.1006/smim.2001.0322 }}</ref> possibly related to the outward transport of the lipid [[platelet activating factor]] (PAF). It has also been reported that ABCB1 mediates transport of [[cortisol]] and [[dexamethasone]], but not of [[progesterone]] in ABCB1 transfected cells. MDR1 can also transport [[cholesterol]], short-chain and long-chain analogs of [[phosphatidylcholine]] (PC), [[phosphatidylethanolamine]] (PE), [[phosphatidylserine]] (PS), [[sphingomyelin]] (SM), and [[glucosylceramide]] (GlcCer). Multispecific transport of diverse endogenous lipids through the MDR1 transporter can possibly affect the transbilayer distribution of lipids, in particular of species normally predominant on the inner plasma membrane leaflet such as PS and PE.<ref name=pohl/>

More recently, ABC-transporters have been shown to exist within the [[placenta]], indicating they could play a protective role for the developing fetus against [[xenobiotic]]s.<ref name=pmid16460798>{{cite journal | vauthors = Gedeon C, Behravan J, Koren G, Piquette-Miller M | title = Transport of glyburide by placental ABC transporters: implications in fetal drug exposure | journal = Placenta | volume = 27 | issue = 11–12 | pages = 1096–102 | year = 2006 | pmid = 16460798 | doi = 10.1016/j.placenta.2005.11.012 }}</ref> Evidence has shown that placental expression of the ABC-transporters P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) are increased in preterm compared to term placentae, with P-gp expression further increased in preterm pregnancies with chorioamnionitis.<ref name="Journal of Clinical Endocrinology and Metabolism v 107">{{Cite journal |last1=Scott |first1=Hailey |last2=Martinelli |first2=Lilian M. |last3=Grynspan |first3=David |last4=Bloise |first4=Enrrico |last5=Connor |first5=Kristin L. |date=2022-03-24 |title=Preterm Birth Associates With Increased Placental Expression of MDR Transporters Irrespective of Prepregnancy BMI |journal=The Journal of Clinical Endocrinology and Metabolism |volume=107 |issue=4 |pages=1140–1158 |doi=10.1210/clinem/dgab813 |issn=1945-7197 |pmid=34748636|s2cid=243863723 |doi-access=free }}</ref> To a lesser extent, increasing maternal BMI also associated with increased placental ABC-transporter expression, but only at preterm.<ref name="Journal of Clinical Endocrinology and Metabolism v 107" />