Steroid hormone receptor

Group of protein families

Steroid hormone receptors are found in the nucleus, cytosol, and also on the plasma membrane of target cells. They are generally intracellular receptors (typically cytoplasmic or nuclear) and initiate signal transduction for steroid hormones which lead to changes in gene expression over a time period of hours to days. The best studied steroid hormone receptors are members of the nuclear receptor subfamily 3 (NR3) that include receptors for estrogen (group NR3A)[1] and 3-ketosteroids (group NR3C).[2] In addition to nuclear receptors, several G protein-coupled receptors and ion channels act as cell surface receptors for certain steroid hormones.

A steroid hormone receptor is a protein molecule located either within the cell cytoplasm or nucleus that specifically binds to steroid hormones, such as estrogen, progesterone, and testosterone, leading to the activation or suppression of gene expression and subsequent cellular responses. This interaction is crucial for mediating the physiological effects of steroid hormones in various tissues and organs of the body.[3]

## Types

[edit]

Steroid hormone receptors can be categorized into several types based on their specific ligands and functions:

1.Estrogen Receptors (ER): There are two subtypes, ERα and ERβ, which bind to the hormone estrogen. They regulate gene expression in response to estrogen, playing essential roles in reproductive tissues, bone metabolism, and cardiovascular health.

2\. Progesterone Receptors (PR): PRs bind to the hormone progesterone and regulate gene expression in response to its signaling. They are critical for various reproductive processes, including menstruation, pregnancy, and mammary gland development.

3\. Androgen Receptors (AR): These receptors bind to androgens such as testosterone and dihydrotestosterone (DHT). They play key roles in the development and function of male reproductive organs, as well as in secondary sexual characteristics and muscle growth.

4\. Glucocorticoid Receptors (GR): GRs bind to glucocorticoids like cortisol and regulate gene expression in response to stress and metabolic signals. They are involved in processes such as immune response, metabolism, and stress adaptation.

5\. Mineralocorticoid Receptors (MR): MRs primarily bind to mineralocorticoids such as aldosterone and regulate electrolyte balance and blood pressure by controlling ion transport in epithelial cells of the kidney and other tissues.[4]

### Nuclear receptors

[edit]

Main article: nuclear receptor

Steroid receptors of the nuclear receptor family are all transcription factors. Depending upon the type of receptor, they are either located in the cytosol and move to the cell nucleus upon activation, or remain in the nucleus waiting for the steroid hormone to enter and activate them. This uptake into the nucleus is facilitated by nuclear localization signal (NLS) found in the hinge region of the receptor. This region of the receptor is covered up by heat shock proteins (HSPs) which bind the receptor until the hormone is present. Upon binding by the hormone the receptor undergoes a conformational change releasing the HSP, and the receptor together with the bound hormone enter the nucleus to act upon transcription.

* Nuclear receptors
* Subfamily 3: Estrogen Receptor-like
* Group A: Estrogen receptor (Sex hormones: Estrogen)
* 1: Estrogen receptor-α (ERα; NR3A1, ESR1)
* 2: Estrogen receptor-β (ERβ; NR3A2, ESR2)
* Group C: 3-Ketosteroid receptors
* 1: Glucocorticoid receptor (GR; NR3C1) (Cortisol)
* 2: Mineralocorticoid receptor (MR; NR3C2) (Aldosterone)
* 3: Progesterone receptor (PR; NR3C3, PGR) (Sex hormones: Progesterone)
* 4: Androgen receptor (AR; NR3C4, AR) (Sex hormones: Testosterone)

#### Structure

[edit]

Intracellular steroid hormone receptors share a common structure of four units that are functionally homologous, so-called "domains":

1. Variable domain: It begins at the N-terminal and is the most variable domain between the different receptors.
2. DNA binding domain: This centrally located highly conserved DNA binding domain (DBD) consists of two non-repetitive globular motifs[5] where zinc is coordinated with four cysteine and no histidine residues. Their secondary and tertiary structure is distinct from that of classic zinc fingers.[6] This region controls which gene will be activated. On DNA it interacts with the hormone response element (HRE).
3. Hinge region: This area controls the movement of the receptor to the nucleus.
4. Hormone binding domain: The moderately conserved ligand-binding domain (LBD) can include a nuclear localization signal, amino-acid sequences capable of binding chaperones and parts of dimerization interfaces. Such receptors are closely related to chaperones (namely heat shock proteins hsp90 and hsp56), which are required to maintain their inactive (but receptive) cytoplasmic conformation. At the end of this domain is the C-terminal. The terminal connects the molecule to its pair in the homodimer or heterodimer. It may affect the magnitude of the response.

#### Mechanism of action

[edit]

##### Genomic

[edit]

Depending on their mechanism of action and subcellular distribution, nuclear receptors may be classified into at least two classes.[7][8] Nuclear receptors that bind steroid hormones are all classified as type I receptors. Only type I receptors have a heat shock protein (HSP) associated with the inactive receptor that will be released when the receptor interacts with the ligand. Type I receptors may be found in homodimer or heterodimer forms. Type II nuclear receptors have no HSP, and in contrast to the classical type I receptor are located in the cell nucleus.

Free (that is, unbound) steroids enter the cell cytoplasm and interact with their receptor. In this process heat shock protein is dissociated, and the activated receptor-ligand complex is translocated into the nucleus. It is also related to EAATs.

After binding to the ligand (steroid hormone), steroid receptors often form dimers. In the nucleus, the complex acts as a transcription factor, augmenting or suppressing transcription particular genes by its action on DNA.

Type II receptors are located in the nucleus. Thus, their ligands pass through the cell membrane and cytoplasm and enter the nucleus where they activate the receptor without release of HSP. The activated receptor interacts with the hormone response element and the transcription process is initiated as with type I receptors.

##### Non-genomic

[edit]

The cell membrane aldosterone receptor has shown to increase the activity of the basolateral Na/K ATPase, ENaC sodium channels and ROMK potassium channels of the principal cell in the distal tubule and cortical collecting duct of nephrons (as well as in the large bowel and possibly in sweat glands).

There is some evidence that certain steroid hormone receptors can extend through lipid bilayer membranes at the surface of cells and might be able to interact with hormones that remain outside cells.[9]

Steroid hormone receptors can also function outside the nucleus and couple to cytoplasmic signal transduction proteins such as PI3k and Akt kinase.[10]

### Other

[edit]

Steroid hormone receptors exert their effects through several mechanisms, including:

1\. Gene Regulation: Upon ligand binding, steroid hormone receptors translocate to the nucleus, where they bind to specific DNA sequences called hormone response elements (HREs) within the regulatory regions of target genes. This binding either activates or suppresses gene transcription, leading to changes in mRNA levels and ultimately protein synthesis.

2\. Transcriptional Coactivators and Corepressors: Steroid hormone receptors recruit coactivator or corepressor proteins to the gene promoter regions, which modulate the activity of RNA polymerase and other transcriptional machinery, thereby influencing gene expression.

3\. Chromatin Remodeling: Steroid hormone receptors can also induce changes in chromatin structure through the recruitment of chromatin remodeling complexes. This allows for accessibility of the transcriptional machinery to specific gene regulatory regions, facilitating or inhibiting gene transcription.

4\. Non-Genomic Signaling: In addition to classical genomic actions, steroid hormone receptors can initiate rapid, non-genomic signaling pathways in the cytoplasm or at the cell membrane. These pathways involve activation of various protein kinases and other signaling molecules, leading to rapid cellular responses such as ion fluxes, cytoskeletal rearrangements, and activation of second messenger systems.

5\. Cross-Talk with Other Signaling Pathways: Steroid hormone receptors can also interact with and modulate the activity of other signaling pathways, such as growth factor signaling pathways, thereby integrating hormonal and growth factor signals to regulate cellular processes.[11]

A new class of steroid hormone receptors has recently been elucidated and these new receptors are found on the cell membrane. New studies suggest that along with the well documented intracellular receptors that cell membrane receptors are present for several steroid hormones and that their cellular responses are much quicker than the intracellular receptors.[12]

#### G protein-coupled receptors

[edit]

GPCR linked proteins most likely interact with steroid hormones through an amino acid consensus sequence traditionally thought of as a cholesterol recognition and interaction site. About a third of Class A GPCRs contain this sequence. The steroid hormones themselves are different enough from one another that they do not all affect all of the GPCR linked proteins; however, the similarities between the steroid hormones and between the receptors make plausible the argument that each receptor may respond to multiple steroid hormones or that each hormone could affect multiple receptors. This is contrary to the traditional model of having a unique receptor for each unique ligand.[13]

At least four different GPCR-linked proteins are known to respond to steroid hormones. GPR30 binds estrogen, membrane progestin receptor (mPR) binds progesterone, and GPRC6A binds androgens. As an example of the effects of these GPCR-linked proteins consider GPR30. GPR30 binds estrogen, and upon binding estrogen this pathway activates adenylyl cyclase and epidermal growth factor receptor. It results in vasodilation, renoprotection, mammary gland development, etc.[13]

Sulfated steroids and bile acids are also detected by vomeronasal receptors, specifically the V1 family.[14][15][16]

#### Ion channels

[edit]

Neuroactive steroids bind to and modulate the activity of several ion channels including the GABAA,[17][18][19][20] NMDA,[21] and sigma receptors.[22]

The steroid progesterone has been found to modulate the activity of CatSper (cation channels of sperm) voltage-gated Ca2+ channels. Since eggs release progesterone, sperm may use progesterone as a homing signal to swim toward eggs (chemotaxis).[23][24]

#### SHBG/SHBG-R complex

[edit]

Sex hormone-binding globulin (SHBG) is thought to mainly function as a transporter and reservoir for the estradiol and testosterone sex hormones. However it has also been demonstrated that SHBG can bind to a cell surface receptor (SHBG-R). The SHBG-R has not been completely characterized. A subset of steroids are able to bind to the SHBG/SHBG-R complex resulting in an activation of adenylyl cyclase and synthesis of the cAMP second messenger.[25] Hence the SHBG/SHBG-R complex appears to act as a transmembrane steroid receptor that is capable of transmitting signals to the interior of cells.

## See also

[edit]

* Membrane steroid receptor
* Nuclear receptor

## References

[edit]

1. ^ Dahlman-Wright K, Cavailles V, Fuqua SA, Jordan VC, Katzenellenbogen JA, Korach KS, Maggi A, Muramatsu M, Parker MG, Gustafsson JA (Dec 2006). "International Union of Pharmacology. LXIV. Estrogen receptors". Pharmacological Reviews. 58 (4): 773–81\. doi:10.1124/pr.58.4.8. PMID 17132854. S2CID 45996586.
2. ^ Lu NZ, Wardell SE, Burnstein KL, Defranco D, Fuller PJ, Giguere V, Hochberg RB, McKay L, Renoir JM, Weigel NL, Wilson EM, McDonnell DP, Cidlowski JA (Dec 2006). "International Union of Pharmacology. LXV. The pharmacology and classification of the nuclear receptor superfamily: glucocorticoid, mineralocorticoid, progesterone, and androgen receptors" (PDF). Pharmacological Reviews. 58 (4): 782–97\. doi:10.1124/pr.58.4.9. PMID 17132855. S2CID 28626145. Archived from the original (PDF) on 2019-02-28.
3. ^ Thornton JW, Need E, Crews D. Resurrecting the ancestral steroid receptor: ancient origin of estrogen signaling. Science. 2003 Jul 4;301(5637):1714-7. doi: 10.1126/science.1086185. PMID 12805548.
4. ^ Evans RM. The steroid and thyroid hormone receptor superfamily. Science. 1988 Nov 18;240(4859):889-95. doi: 10.1126/science.3283939. PMID 3283939.
5. ^ PDB: 1HCQ​; Schwabe JW, Chapman L, Finch JT, Rhodes D (Nov 1993). "The crystal structure of the estrogen receptor DNA-binding domain bound to DNA: how receptors discriminate between their response elements". Cell. 75 (3): 567–78\. doi:10.1016/0092-8674(93)90390-C. PMID 8221895. S2CID 20795587.
6. ^ Evans RM (May 1988). "The steroid and thyroid hormone receptor superfamily". Science. 240 (4854): 889–95\. Bibcode:1988Sci...240..889E. doi:10.1126/science.3283939. PMC 6159881. PMID 3283939.
7. ^ Mangelsdorf DJ, Thummel C, Beato M, Herrlich P, Schütz G, Umesono K, Blumberg B, Kastner P, Mark M, Chambon P, Evans RM (Dec 1995). "The nuclear receptor superfamily: the second decade". Cell. 83 (6): 835–9\. doi:10.1016/0092-8674(95)90199-X. PMC 6159888. PMID 8521507.
8. ^ Novac N, Heinzel T (Dec 2004). "Nuclear receptors: overview and classification". Current Drug Targets. Inflammation and Allergy. 3 (4): 335–46\. doi:10.2174/1568010042634541. PMID 15584884.
9. ^ Luconi M, Francavilla F, Porazzi I, Macerola B, Forti G, Baldi E (Aug 2004). "Human spermatozoa as a model for studying membrane receptors mediating rapid nongenomic effects of progesterone and estrogens". Steroids. 69 (8–9): 553–9\. doi:10.1016/j.steroids.2004.05.013. PMID 15288769. S2CID 25453428.8–9&rft.pages=553-9&rft.date=2004-08&rft_id=https://api.semanticscholar.org/CorpusID:25453428#id-name=S2CID&rft_id=info:pmid/15288769&rft_id=info:doi/10.1016/j.steroids.2004.05.013&rft.aulast=Luconi&rft.aufirst=M&rft.au=Francavilla,+F&rft.au=Porazzi,+I&rft.au=Macerola,+B&rft.au=Forti,+G&rft.au=Baldi,+E&rfr_id=info:sid/en.wikipedia.org:Steroid+hormone+receptor" class="Z3988">
10. ^ Aquila S, Sisci D, Gentile M, Middea E, Catalano S, Carpino A, Rago V, Andò S (Mar 2004). "Estrogen receptor (ER)alpha and ER beta are both expressed in human ejaculated spermatozoa: evidence of their direct interaction with phosphatidylinositol-3-OH kinase/Akt pathway". The Journal of Clinical Endocrinology and Metabolism. 89 (3): 1443–51\. doi:10.1210/jc.2003-031681. PMID 15001646.
11. ^ Mangelsdorf DJ, Thummel C, Beato M, Herrlich P, Schütz G, Umesono K, Blumberg B, Kastner P, Mark M, Chambon P, Evans RM. The nuclear receptor superfamily: the second decade. Cell. 1995 Dec 15;83(6):835-9. doi: 10.1016/0092-8674(95)90199-x. PMID 8521507.
12. ^ Norman AW, Mizwicki MT, Norman DP (Jan 2004). "Steroid-hormone rapid actions, membrane receptors and a conformational ensemble model". Nature Reviews. Drug Discovery. 3 (1): 27–41\. doi:10.1038/nrd1283. PMID 14708019. S2CID 17487277.
13. ^ a b Wang C, Liu Y, Cao JM (2014). "G protein-coupled receptors: extranuclear mediators for the non-genomic actions of steroids". International Journal of Molecular Sciences. 15 (9): 15412–25\. doi:10.3390/ijms150915412. PMC 4200746. PMID 25257522.
14. ^ Lee D, Kume M, Holy TE (December 2019). "Sensory coding mechanisms revealed by optical tagging of physiologically defined neuronal types". Science. 366 (6471): 1384–1389\. Bibcode:2019Sci...366.1384L. doi:10.1126/science.aax8055. PMC 7591936. PMID 31831669. S2CID 209339279.
15. ^ Haga-Yamanaka S, Ma L, He J, Qiu Q, Lavis LD, Looger LL, Yu CR (July 2014). "Integrated action of pheromone signals in promoting courtship behavior in male mice". eLife. 3: e03025. doi:10.7554/eLife.03025. PMC 4107909. PMID 25073926.
16. ^ Wong WM, Cao J, Zhang X, Doyle WI, Mercado LL, Gautron L, Meeks JP (May 2020). "Physiology-forward identification of bile acid-sensitive vomeronasal receptors". Sci Adv. 6 (22): eaaz6868. Bibcode:2020SciA....6.6868W. doi:10.1126/sciadv.aaz6868. PMC 7259934. PMID 32523992.
17. ^ Majewska MD, Harrison NL, Schwartz RD, Barker JL, Paul SM (May 1986). "Steroid hormone metabolites are barbiturate-like modulators of the GABA receptor". Science. 232 (4753): 1004–7\. doi:10.1126/science.2422758. PMID 2422758.
18. ^ Herd MB, Belelli D, Lambert JJ (Oct 2007). "Neurosteroid modulation of synaptic and extrasynaptic GABA(A) receptors". Pharmacology & Therapeutics. 116 (1): 20–34\. arXiv:1607.02870. doi:10.1016/j.pharmthera.2007.03.007. PMID 17531325.
19. ^ Hosie AM, Wilkins ME, da Silva HM, Smart TG (Nov 2006). "Endogenous neurosteroids regulate GABAA receptors through two discrete transmembrane sites". Nature. 444 (7118): 486–9\. Bibcode:2006Natur.444..486H. doi:10.1038/nature05324. PMID 17108970. S2CID 4382394.
20. ^ Puia G, Santi MR, Vicini S, Pritchett DB, Purdy RH, Paul SM, Seeburg PH, Costa E (May 1990). "Neurosteroids act on recombinant human GABAA receptors". Neuron. 4 (5): 759–65\. doi:10.1016/0896-6273(90)90202-Q. PMID 2160838. S2CID 12626366.
21. ^ Wu FS, Gibbs TT, Farb DH (Sep 1991). "Pregnenolone sulfate: a positive allosteric modulator at the N-methyl-D-aspartate receptor" (abstract). Molecular Pharmacology. 40 (3): 333–6\. doi:10.1016/S0026-895X(25)12923-4. PMID 1654510.
22. ^ Maurice T, Junien JL, Privat A (Feb 1997). "Dehydroepiandrosterone sulfate attenuates dizocilpine-induced learning impairment in mice via sigma 1-receptors". Behavioural Brain Research. 83 (1–2): 159–64\. doi:10.1016/S0166-4328(97)86061-5. PMID 9062676. S2CID 3979800.1–2&rft.pages=159-64&rft.date=1997-02&rft_id=https://api.semanticscholar.org/CorpusID:3979800#id-name=S2CID&rft_id=info:pmid/9062676&rft_id=info:doi/10.1016/S0166-4328(97)86061-5&rft.aulast=Maurice&rft.aufirst=T&rft.au=Junien,+JL&rft.au=Privat,+A&rfr_id=info:sid/en.wikipedia.org:Steroid+hormone+receptor" class="Z3988">
23. ^ Strünker T, Goodwin N, Brenker C, Kashikar ND, Weyand I, Seifert R, Kaupp UB (Mar 2011). "The CatSper channel mediates progesterone-induced Ca2+ influx in human sperm". Nature. 471 (7338): 382–6\. Bibcode:2011Natur.471..382S. doi:10.1038/nature09769. PMID 21412338. S2CID 4431334.
* Ewen Callaway (16 March 2011). "Female hormone could be key to male contraceptive". Nature. doi:10.1038/news.2011.163.
24. ^ Lishko PV, Botchkina IL, Kirichok Y (Mar 2011). "Progesterone activates the principal Ca2+ channel of human sperm". Nature. 471 (7338): 387–91\. Bibcode:2011Natur.471..387L. doi:10.1038/nature09767. PMID 21412339. S2CID 4340309.
25. ^ Rosner W, Hryb DJ, Kahn SM, Nakhla AM, Romas NA (Mar 2010). "Interactions of sex hormone-binding globulin with target cells". Molecular and Cellular Endocrinology. 316 (1): 79–85\. doi:10.1016/j.mce.2009.08.009. PMID 19698759. S2CID 27912941.

## External links

[edit]

* Steroid+Receptors at the U.S. National Library of Medicine Medical Subject Headings (MeSH)
* Messer WS (3 April 2000). "MBC 3320 Steroid hormones and receptors". The University of Toledo. Archived from the original on 17 April 2008.

* v
* t
* e

Transcription factors and intracellular receptors

(1) Basic domains

| (1.1) Basic leucine zipper (bZIP)|

* Activating transcription factor
* AATF
* 1
* 2
* 3
* 4
* 5
* 6
* 7
* AP-1
* c-Fos
* FOSB
* FOSL1
* FOSL2
* JDP2
* c-Jun
* JUNB
* JunD
* BACH
* 1
* 2
* BATF
* BLZF1
* C/EBP
* α
* β
* γ
* δ
* ε
* ζ
* CREB
* 1
* 3
* L1
* CREM
* DBP
* DDIT3
* GABPA
* GCN4
* HLF
* MAF
* B
* sMaf
* F
* G
* K
* NFE
* 2
* L1
* L2
* L3
* NFIL3
* NRL
* NRF
* 1
* 2
* 3
* XBP1

|

(1.2) Basic helix-loop-helix (bHLH)|

| Group A|

* AS-C
* ASCL1
* ASCL2
* ATOH1
* HAND
* 1
* 2
* MESP2
* Myogenic regulatory factors
* MyoD
* Myogenin
* MYF5
* MYF6
* NeuroD
* 1
* 2
* Neurogenins
* 1
* 2
* 3
* OLIG
* 1
* 2
* Paraxis
* TCF15
* Scleraxis
* SLC
* LYL1
* TAL
* 1
* 2
* Twist

|

Group B|

* FIGLA
* Myc
* c-Myc
* l-Myc
* n-Myc
* MXD4
* TCF4

Group C
bHLH-PAS|

* AhR
* AHRR
* ARNT
* ARNTL
* ARNTL2
* CLOCK
* HIF
* 1A
* EPAS1
* 3A
* NPAS
* 1
* 2
* 3
* PER
* 1
* 2
* 3
* Period
* SIM
* 1
* 2

Group D|

* BHLH
* 2
* 3
* 9
* Pho4
* ID
* 1
* 2
* 3
* 4

Group E|

* HES
* 1
* 2
* 3
* 4
* 5
* 6
* 7
* HEY
* 1
* 2
* L

Group F
bHLH-COE|

* EBF1

(1.3) bHLH-ZIP|

* AP-4
* MAX
* MXD1
* MXD3
* MITF
* MNT
* MLX
* MLXIPL
* MXI1
* Myc
* SREBP
* 1
* 2
* USF1

(1.4) NF-1|

* NFI
* A
* B
* C
* X
* SMAD
* R-SMAD
* 1
* 2
* 3
* 5
* 9
* I-SMAD
* 6
* 7
* 4)

(1.5) RF-X|

* RFX
* 1
* 2
* 3
* 4
* 5
* 6
* ANK

(1.6) Basic helix-span-helix (bHSH)|

* AP-2
* α
* β
* γ
* δ
* ε

(2) Zinc finger DNA-binding domains

| (2.1) Nuclear receptor (Cys4)|

| subfamily 1|

* Thyroid hormone
* α
* β
* CAR
* FXR
* LXR
* α
* β
* PPAR
* α
* β/δ
* γ
* PXR
* RAR
* α
* β
* γ
* ROR
* α
* β
* γ
* Rev-ErbA
* α
* β
* VDR

|

subfamily 2|

* COUP-TF
* (I
* II
* Ear-2
* HNF4
* α
* γ
* PNR
* RXR
* α
* β
* γ
* Testicular receptor
* 2
* 4
* TLX

subfamily 3|

* Steroid hormone
* Androgen
* Estrogen
* α
* β
* Glucocorticoid
* Mineralocorticoid
* Progesterone
* Estrogen related
* α
* β
* γ

subfamily 4|

* NUR
* NGFIB
* NOR1
* NURR1

subfamily 5|

* LRH-1
* SF1

subfamily 6|

* GCNF

subfamily 0|

* DAX1
* SHP

(2.2) Other Cys4|

* GATA
* 1
* 2
* 3
* 4
* 5
* 6
* MTA
* 1
* 2
* 3
* TRPS1

(2.3) Cys2His2|

* General transcription factors
* TFIIA
* TFIIB
* TFIID
* TFIIE
* 1
* 2
* TFIIF
* 1
* 2
* TFIIH
* 1
* 2
* 4
* 2I
* 3A
* 3C1
* 3C2

* ATBF1
* BCL
* 6
* 11A
* 11B
* CTCF
* E4F1
* EGR
* 1
* 2
* 3
* 4
* ERV3
* GFI1
* GLI family
* 1
* 2
* 3
* REST
* S1
* S2
* YY1
* HIC
* 1
* 2
* HIVEP
* 1
* 2
* 3
* IKZF
* 1
* 2
* 3
* ILF
* 2
* 3
* Sp/KLF family
* KLF
* 1
* 2
* 3
* 4
* 5
* 6
* 7
* 8
* 9
* 10
* 11
* 12
* 13
* 14
* 15
* 17
* SP
* 1
* 2
* 4
* 7
* 8
* MTF1
* MYT1
* OSR1
* PRDM9
* SALL
* 1
* 2
* 3
* 4
* TSHZ3
* WT1
* Zbtb7
* 7A
* 7B
* ZBTB
* 11
* 16
* 17
* 20
* 21
* 32
* 33
* 40
* zinc finger
* 3
* 7
* 9
* 10
* 19
* 22
* 24
* 33B
* 34
* 35
* 41
* 43
* 44
* 51
* 74
* 143
* 146
* 148
* 165
* 202
* 217
* 219
* 238
* 239
* 259
* 267
* 268
* 281
* 300
* 318
* 330
* 346
* 350
* 365
* 366
* 384
* 423
* 451
* 452
* 471
* 593
* 638
* 644
* 649
* 655
* 804A

(2.4) Cys6|

* HIVEP1

(2.5) Alternating composition|

* AIRE
* DIDO1
* GRLF1
* ING
* 1
* 2
* 4
* JARID
* 1A
* 1B
* 1C
* 1D
* 2
* JMJD1B

(2.6) WRKY|

* WRKY

(3) Helix-turn-helix domains

| (3.1) Homeodomain|

| Antennapedia
ANTP class|

| protoHOX
Hox-like|

* ParaHox
* Gsx
* 1
* 2
* Xlox
* PDX1
* Cdx
* 1
* 2
* 4
* extended Hox: Evx1
* Evx2
* MEOX1
* MEOX2
* Homeobox
* A1
* A2
* A3
* A4
* A5
* A7
* A9
* A10
* A11
* A13
* B1
* B2
* B3
* B4
* B5
* B6
* B7
* B8
* B9
* B13
* C4
* C5
* C6
* C8
* C9
* C10
* C11
* C12
* C13
* D1
* D3
* D4
* D8
* D9
* D10
* D11
* D12
* D13
* GBX1
* GBX2
* MNX1

|

metaHOX
NK-like|

* BARHL1
* BARHL2
* BARX1
* BARX2
* BSX
* DBX
* 1
* 2
* DLX
* 1
* 2
* 3
* 4
* 5
* 6
* EMX
* 1
* 2
* EN
* 1
* 2
* HHEX
* HLX
* LBX1
* LBX2
* MSX
* 1
* 2
* NANOG
* NKX
* 2-1
* 2-2
* 2-3
* 2-5
* 3-1
* 3-2
* HMX1
* HMX2
* HMX3
* 6-1
* 6-2
* NOTO
* TLX1
* TLX2
* TLX3
* VAX1
* VAX2

other|

* ARX
* CRX
* CUTL1
* FHL
* 1
* 2
* 3
* HESX1
* HOPX
* LMX
* 1A
* 1B
* NOBOX
* TALE
* IRX
* 1
* 2
* 3
* 4
* 5
* 6
* MKX
* MEIS
* 1
* 2
* PBX
* 1
* 2
* 3
* PKNOX
* 1
* 2
* SIX
* 1
* 2
* 3
* 4
* 5
* PHF
* 1
* 3
* 6
* 8
* 10
* 16
* 17
* 20
* 21A
* POU domain
* PIT-1
* BRN-3: A
* B
* C
* Octamer transcription factor: 1
* 2
* 3/4
* 6
* 7
* 11
* SATB2
* ZEB
* 1
* 2

(3.2) Paired box|

* PAX
* 1
* 2
* 3
* 4
* 5
* 6
* 7
* 8
* 9
* PRRX
* 1
* 2
* PROP1
* PHOX
* 2A
* 2B
* RAX
* SHOX
* SHOX2
* VSX1
* VSX2
* Bicoid
* GSC
* BICD2
* OTX
* 1
* 2
* PITX
* 1
* 2
* 3

(3.3) Fork head / winged helix|

* E2F
* 1
* 2
* 3
* 4
* 5
* FOX proteins
* A1
* A2
* A3
* B1
* B2
* C1
* C2
* D1
* D2
* D3
* D4
* D4L1
* D4L3
* D4L4
* D4L5
* D4L6
* E1
* E3
* F1
* F2
* G1
* H1
* I1
* I2
* I3
* J1
* J2
* J3
* K1
* K2
* L1
* L2
* M1
* N1
* N2
* N3
* N4
* O1
* O3
* O4
* O6
* P1
* P2
* P3
* P4
* Q1
* R1
* R2
* S1

(3.4) Heat shock factors|

* HSF
* 1
* 2
* 4

(3.5) Tryptophan clusters|

* ELF
* 2
* 4
* 5
* EHF
* ELK
* 1
* 3
* 4
* ERF
* ETS
* 1
* 2
* ERG
* SPIB
* ETV
* 1
* 4
* 5
* 6
* FLI1
* Interferon regulatory factors
* 1
* 2
* 3
* 4
* 5
* 6
* 7
* 8
* MYB
* MYBL2

(3.6) TEA domain|

* transcriptional enhancer factor
* 1
* 2
* 3
* 4

(4) β-Scaffold factors with minor groove contacts

| (4.1) Rel homology region|

* NF-κB
* NFKB1
* NFKB2
* REL
* RELA
* RELB
* NFAT
* C1
* C2
* C3
* C4
* 5

|

(4.2) STAT|

* STAT
* 1
* 2
* 3
* 4
* 5
* 6

(4.3) p53-like|

* p53 p63 p73 family
* p53
* TP63
* p73
* TBX
* 1
* 2
* 3
* 5
* 19
* 21
* 22
* TBR1
* TBR2
* TFT
* MYRF

(4.4) MADS box|

* Mef2
* A
* B
* C
* D
* SRF

(4.6) TATA-binding proteins|

* TBP
* TBPL1

(4.7) High-mobility group|

* BBX
* HMGB
* 1
* 2
* 3
* 4
* HMGN
* 1
* 2
* 3
* 4
* HNF
* 1A
* 1B
* SOX
* 1
* 2
* 3
* 4
* 5
* 6
* 8
* 9
* 10
* 11
* 12
* 13
* 14
* 15
* 17
* 18
* 21
* SRY
* SSRP1
* TCF/LEF
* TCF
* 1
* 3
* 4
* LEF1
* TOX
* 1
* 2
* 3
* 4

(4.9) Grainyhead|

* TFCP2

(4.10) Cold-shock domain|

* CSDA
* YBX1

(4.11) Runt|

* CBF
* CBFA2T2
* CBFA2T3
* RUNX1
* RUNX2
* RUNX3
* RUNX1T1

(0) Other transcription factors

| (0.2) HMGI(Y)|

* HMGA
* 1
* 2
* HBP1

|

(0.3) Pocket domain|

* Rb
* RBL1
* RBL2

(0.5) AP-2/EREBP-related factors|

* Apetala 2
* EREBP
* B3

(0.6) Miscellaneous|

* ARID
* 1A
* 1B
* 2
* 3A
* 3B
* 4A
* CAP
* IFI
* 16
* 35
* MLL
* 2
* 3
* T1
* MNDA
* NFY
* A
* B
* C
* Rho/Sigma

see also transcription factor/coregulator deficiencies

* v
* t
* e

Receptor/signaling modulators

Amino acids and
similar/related|

* Amino acids and related: GABA receptor modulators
* GABAA receptor positive modulators
* GABA metabolism and transport modulators
* GHB receptor modulators
* Glutamate metabolism and transport modulators
* Glycine receptor modulators
* Ionotropic glutamate receptor modulators
* Metabotropic glutamate receptor modulators

* Monoamines: Adrenergic receptor modulators
* Dopamine receptor modulators
* Histamine receptor modulators
* Melatonin receptor modulators
* Monoamine metabolism modulators
* Monoamine neurotoxins
* Monoamine releasing agents
* Monoamine reuptake inhibitors
* Serotonin receptor modulators
* hTAAR modulators

* Acetylcholine: Acetylcholine metabolism and transport modulators
* Muscarinic acetylcholine receptor modulators
* Nicotinic acetylcholine receptor modulators

* Others: Imidazoline receptor modulators
* Purine receptor modulators
* Sigma receptor modulators
* Thyroid hormone receptor modulators

Lipids|

* Eicosanoids: Cannabinoid receptor modulators
* Leukotriene signaling modulators
* Prostanoid signaling modulators

* Phospholipids: Lysophospholipid signaling modulators
* PAF receptor modulators

* Steroids: Androgen receptor modulators
* Estrogen receptor modulators
* Glucocorticoid receptor modulators
* Mineralocorticoid receptor modulators
* Progesterone receptor modulators
* Steroid metabolism modulators

* Other nuclear receptors: Aryl hydrocarbon receptor modulators
* Estrogen-related receptor modulators
* FXR and LXR modulators
* PPAR modulators
* Retinoid receptor modulators
* Vitamin D receptor modulators
* Xenobiotic-sensing receptor modulators

Peptides/proteins|

* Peptides: Angiotensin receptor modulators
* GH/IGF-1 axis signaling modulators
* GnRH and gonadotropin receptor modulators
* Melanocortin receptor modulators
* Neurokinin receptor modulators
* Opioid receptor modulators
* Oxytocin and vasopressin receptor modulators

* Cytokines: Cytokine receptor modulators
* Chemokine receptor modulators
* Interleukin receptor modulators
* TNF receptor superfamily modulators

* Growth factors: Growth factor receptor modulators
* TGFβ receptor superfamily modulators

Others and
non-receptor|

* Enzymes: Cytochrome P450 modulators
* Histone deacetylase inhibitors
* Phosphodiesterase inhibitors

* Ion channels: Ion channel modulators
* TRP channel modulators

* Transporters: Sodium-glucose transporter modulators
* Symporter inhibitors

* Others: Nitric oxide signaling modulators

*[v]: View this template
*[t]: Discuss this template
*[e]: Edit this template
*[GABA]: γ-Aminobutyric acid
*[GABAA]: γ-Aminobutyric acid A
*[GHB]: γ-Hydroxybutyric acid
*[hTAAR]: human trace amine-associated receptor
*[PAF]: Platelet-activating factor
*[FXR]: Farnesoid X receptor
*[LXR]: Liver X receptor
*[PPAR]: Peroxisome proliferator-activated receptor
*[GH]: Growth hormone
*[IGF-1]: Insulin-like growth factor 1
*[GnRH]: gonadotropin hormone-releasing hormone
*[TNF]: Tumor necrosis factor
*[TGFβ]: Transforming growth factor beta
*[TRP]: Transient receptor potential