TheProfessor
Member
I'd prefer to multi-post this to get more viewers but I don't want to get flamed, Ill repost this in the anabolics forum and just remote them back here.
1. I want as many questions as possible
2. I don't know where this thread belongs.
Mods can relocate or delete as they wish.
I am currently doing a literature review of the androgen receptor for undisclosed purposes. While the information is fresh in my head and while I am still seeking out more, people are more than welcome to ask me ANYTHING that involves the androgen receptor, as technical or as non-technical as they want. I might know off hand, if I don't I'll look it up. More information for me. I'll attempt to provide the source with every answer I give as well if you want.
Fire!!
Regards
Howabout I give you guys some help!
Here are some bullets I am accumulating, It will grow longer and longer, but it might be a basis for some questions!
Anything you ever wanted to know (and likely more) about the androgen receptor (this will get filled in as I have the time)
Androgen Receptor:
Intro:
-Member of the steroid and nuclear receptor superfamily (>100 members)
-Only 5 vertebrate steroid receptors are known
-Estrogen (two types)
-Alpha and Beta subtypes
-Progesterone
-Androgen
-only one androgen receptor gene found in humans
-Glucocorticoid
-Mineralocorticoid
-Androgen receptor gene:
- >90kb and codes for a protein 919 AA with 3 major functional domains:
-N-Terminal Domain (NTD)
-Modulatory function encoded by exon 1
-DNA binding domain (DBD)
-Exons 2 and 3
-Ligand Binding Domain (LBD)
-Encoded by 5 exons
-Hinge region between DNA binding and Ligand Binding domains
-Two transactivation functions
-N-Terminal activation function (AF1)
-Constitutive in truncated receptor (lacking LBD)
-Sequence not conserved compared to other steroid receptors
-C-Terminal activation function (AF2)
-Ligand-dependant (conserved sequence) in regard to charge-clamp residues
-Androgen receptor activation:
-Soluble, complexed with heat shot proteins, acts as an intracellular transcription factor
-Androgen binds causing conformational changes
-Agonist binding induces conformational change that allows for activation of AF2 that is crucial for co
regulator recruitment (due to a LxxLL motif that co-regulators bind to) and N/C terminus interaction that
may further stabilize the agonist-bound ligand-binding domain.
-DHT-bound AR prefers the binding of FxxLF motifs to that of LxxLL, suggesting that N/C interaction is
preferred over co-activator recruitment (FxxLF competes for AF2 domain)
-HSP dissociates and transformed AR undergoes dimerization, phosphorylation, and then translocation to
the nucleus. Mediated by the nuclear localization signal.
-The translocated receptor binds to the androgen response element (promoter or enhancer of AR gene
targets)
-Co-activators and co-repressors are also involved; the ligand-binding domain mediates
-Both steroidal and non-steroidal compounds may interact with the AR
-May agonize (activate transcription)
-Antagonize (inhibit transcription)
-Nongenomic pathway of AR <--- To be further developed
-AR responds to BOTH androgen AND signal transduction pathways
-has been reported in oocytes, skeletal muscle, osteoblasts, and prostate cancer cells. (Distinguished due to interaction with plasma membrane-associated signaling pathways)
-AR is most expressed in androgen target tissues:
-Prostate
-Skeletal muscle
-Liver
-Central Nervous system
- Epididymis (duct behind testes) (most highly expressed)
- Adrenal Gland (cool!) (Most highly expressed)
-Tissue uptake efficiency and selectivity of different ligands seemed to be related to their binding affinity to AR and their resistance to metabolism
Post Translational Modification of the AR:
There are 23 known sites of direct androgen receptor post-translational modification and greater than 80% of this modification sites affect transcriptional activity in some way. While others my concurrently affect stability, growth ?, and localization.
Modifications include
-Phosphorylation (mostly)
-Acetylation
-Methylation
-SUMOylation
-Ubiquitination
-Dominating hypothesis regarding phosphorylation is that phosphorylation INCREASES as androgrens bind, as
conformational changes expose phosphorylation sites.
-Phosphorylation is hypothesized to affect AR activity by increasing or decreasing protein interactions that occur
proximal to the phosphosite.
-phosphosites have been observed in all 3 main domains of the AR as well as the AFI (hormone independent
coactivation domain) and AF2 (Hormone dependent)
-Some sites may be constitutively phosphorylated
-Some sites may be phosphorylated or de-phosphorylated in conjunction with androgen binding indicating
there might be some links.
-Phosphorylation is both dependent on location and CAUSING translocation (likely)
-mutants at phosphorylation sites change transcriptional and translocational activity
-Very interesting, the androgen receptor can be activated WITHOUT the binding of a ligand in certain kinase cascades or at least, sensitize the AR to lower levels of androgen.
-Goal(s) and Missing links
-Developing compounds that can separate the androgenic and anabolic effects of typical AR ligand. Previously thought impossible, due to the genes that the AR governs and the reliance on a SINGLE androgen receptor.
Androgenic- prostate, seminal vesicle, testes (et al)
Anabolic- Nitrogen retaining effects in muscle and bone
-No crystal structure of full-length receptor
-Preference of the AR for N/C terminus interaction for drug targets (opposite of other steroid receptors)
-N/C interaction promotes transcription. A weaker binding compound might favor the AF2 domain to interact
with other peptides besides the AR due to different conformations.
-Structural basis for non-genomic interactions is not clear
-Separation of the genomic and nongenomic functions of steroid receptors unspecific ligands was proposed as a new strategy to achieve tissue selectivity. Structural features that determine this have not been determined.
-Crystal structures of the ligand bound AR exist for both testosterone and DHT, but there is little observable difference, this is strange considering the ridiculous differences is causes gene expression in the prostate.
-How do the post-translational modifications of the receptor affect the transcriptional activities? Is the post-translational modification tissue dependent? If so does this cause the differential affects of DHT in the sex organs?
1. I want as many questions as possible
2. I don't know where this thread belongs.
Mods can relocate or delete as they wish.
I am currently doing a literature review of the androgen receptor for undisclosed purposes. While the information is fresh in my head and while I am still seeking out more, people are more than welcome to ask me ANYTHING that involves the androgen receptor, as technical or as non-technical as they want. I might know off hand, if I don't I'll look it up. More information for me. I'll attempt to provide the source with every answer I give as well if you want.
Fire!!
Regards
Howabout I give you guys some help!
Here are some bullets I am accumulating, It will grow longer and longer, but it might be a basis for some questions!
Anything you ever wanted to know (and likely more) about the androgen receptor (this will get filled in as I have the time)
Androgen Receptor:
Intro:
-Member of the steroid and nuclear receptor superfamily (>100 members)
-Only 5 vertebrate steroid receptors are known
-Estrogen (two types)
-Alpha and Beta subtypes
-Progesterone
-Androgen
-only one androgen receptor gene found in humans
-Glucocorticoid
-Mineralocorticoid
-Androgen receptor gene:
- >90kb and codes for a protein 919 AA with 3 major functional domains:
-N-Terminal Domain (NTD)
-Modulatory function encoded by exon 1
-DNA binding domain (DBD)
-Exons 2 and 3
-Ligand Binding Domain (LBD)
-Encoded by 5 exons
-Hinge region between DNA binding and Ligand Binding domains
-Two transactivation functions
-N-Terminal activation function (AF1)
-Constitutive in truncated receptor (lacking LBD)
-Sequence not conserved compared to other steroid receptors
-C-Terminal activation function (AF2)
-Ligand-dependant (conserved sequence) in regard to charge-clamp residues
-Androgen receptor activation:
-Soluble, complexed with heat shot proteins, acts as an intracellular transcription factor
-Androgen binds causing conformational changes
-Agonist binding induces conformational change that allows for activation of AF2 that is crucial for co
regulator recruitment (due to a LxxLL motif that co-regulators bind to) and N/C terminus interaction that
may further stabilize the agonist-bound ligand-binding domain.
-DHT-bound AR prefers the binding of FxxLF motifs to that of LxxLL, suggesting that N/C interaction is
preferred over co-activator recruitment (FxxLF competes for AF2 domain)
-HSP dissociates and transformed AR undergoes dimerization, phosphorylation, and then translocation to
the nucleus. Mediated by the nuclear localization signal.
-The translocated receptor binds to the androgen response element (promoter or enhancer of AR gene
targets)
-Co-activators and co-repressors are also involved; the ligand-binding domain mediates
-Both steroidal and non-steroidal compounds may interact with the AR
-May agonize (activate transcription)
-Antagonize (inhibit transcription)
-Nongenomic pathway of AR <--- To be further developed
-AR responds to BOTH androgen AND signal transduction pathways
-has been reported in oocytes, skeletal muscle, osteoblasts, and prostate cancer cells. (Distinguished due to interaction with plasma membrane-associated signaling pathways)
-AR is most expressed in androgen target tissues:
-Prostate
-Skeletal muscle
-Liver
-Central Nervous system
- Epididymis (duct behind testes) (most highly expressed)
- Adrenal Gland (cool!) (Most highly expressed)
-Tissue uptake efficiency and selectivity of different ligands seemed to be related to their binding affinity to AR and their resistance to metabolism
Post Translational Modification of the AR:
There are 23 known sites of direct androgen receptor post-translational modification and greater than 80% of this modification sites affect transcriptional activity in some way. While others my concurrently affect stability, growth ?, and localization.
Modifications include
-Phosphorylation (mostly)
-Acetylation
-Methylation
-SUMOylation
-Ubiquitination
-Dominating hypothesis regarding phosphorylation is that phosphorylation INCREASES as androgrens bind, as
conformational changes expose phosphorylation sites.
-Phosphorylation is hypothesized to affect AR activity by increasing or decreasing protein interactions that occur
proximal to the phosphosite.
-phosphosites have been observed in all 3 main domains of the AR as well as the AFI (hormone independent
coactivation domain) and AF2 (Hormone dependent)
-Some sites may be constitutively phosphorylated
-Some sites may be phosphorylated or de-phosphorylated in conjunction with androgen binding indicating
there might be some links.
-Phosphorylation is both dependent on location and CAUSING translocation (likely)
-mutants at phosphorylation sites change transcriptional and translocational activity
-Very interesting, the androgen receptor can be activated WITHOUT the binding of a ligand in certain kinase cascades or at least, sensitize the AR to lower levels of androgen.
-Goal(s) and Missing links
-Developing compounds that can separate the androgenic and anabolic effects of typical AR ligand. Previously thought impossible, due to the genes that the AR governs and the reliance on a SINGLE androgen receptor.
Androgenic- prostate, seminal vesicle, testes (et al)
Anabolic- Nitrogen retaining effects in muscle and bone
-No crystal structure of full-length receptor
-Preference of the AR for N/C terminus interaction for drug targets (opposite of other steroid receptors)
-N/C interaction promotes transcription. A weaker binding compound might favor the AF2 domain to interact
with other peptides besides the AR due to different conformations.
-Structural basis for non-genomic interactions is not clear
-Separation of the genomic and nongenomic functions of steroid receptors unspecific ligands was proposed as a new strategy to achieve tissue selectivity. Structural features that determine this have not been determined.
-Crystal structures of the ligand bound AR exist for both testosterone and DHT, but there is little observable difference, this is strange considering the ridiculous differences is causes gene expression in the prostate.
-How do the post-translational modifications of the receptor affect the transcriptional activities? Is the post-translational modification tissue dependent? If so does this cause the differential affects of DHT in the sex organs?
