Notifications
Clear all
Questions About Steroids
12
Posts
3
Users
0
Likes
1,211
Views
Topic starter
28/06/2019 2:23 pm
Role of the Steroid Receptor Coactivator SRC-3 in Cell Growth.
Ge Zhou,Yoshihiro Hashimoto,Inseok Kwak,Sophia Y. Tsai,and Ming-Jer Tsai
Department of Molecular and Cellular Biology,1 Department of Medicine, Baylor College of Medicine, Houston, Texas 770302
Steroid receptor coactivator 3 (SRC-3/p/CIP/AIB1/ACTR/RAC3/TRAM-1) is a member of the p160 family of nuclear receptor coactivators, which includes SRC-1 (NCoA-1) and SRC-2 (TIF2/GRIP1/NCoA2). Previous studies indicate that SRC-3 is required for normal animal growth and is often amplified or overexpressed in many cancers, including breast and prostate cancers. However, the mechanisms of SRC-3-mediated growth regulation remain unclear. In this study, we show that overexpression of SRC-3 stimulates cell growth to increase cell size in prostate cancer cell lines. Furthermore, our results indicate that overexpression of SRC-3 can modulate the AKT signaling pathway in a steroid-independent manner, which results in the activation of AKT/mTOR signaling concomitant with an increase in cell size. In contrast, down-regulation of SRC-3 expression in cells by small interfering RNA decreases cell growth, leading to a smaller cell size. Similarly, in SRC-3 null mutant mice, AKT signaling is down-regulated in normally SRC-3-expressing tissues. Taken together, these results suggest that SRC-3 is an important modulator for mammalian cell growth.
Genes Dev. 2000 May 15;14(10):1209-28.
The steroid receptor coactivator, GRIP-1, is necessary for MEF-2C-dependent gene expression and skeletal muscle differentiation.
Chen SL, Dowhan DH, Hosking BM, Muscat GE.
University of Queensland, Institute for Molecular Biosciences, Centre for Molecular and Cellular Biology, Ritchie Research Laboratories, B402A, St. Lucia, 4072, Queensland, Australia.
Nuclear receptor-mediated activation of transcription involves coactivation by cofactors collectively denoted the steroid receptor coactivators (SRCs). The process also involves the subsequent recruitment of p300/CBP and PCAF to a complex that synergistically regulates transcription and remodels the chromatin. PCAF and p300 have also been demonstrated to function as critical coactivators for the muscle-specific basic helix-loop-helix (bHLH) protein MyoD during myogenic commitment. Skeletal muscle differentiation and the activation of muscle-specific gene expression is dependent on the concerted action of another bHLH factor, myogenin, and the MADS protein, MEF-2, which function in a cooperative manner. We examined the functional role of one SRC, GRIP-1, in muscle differentiation, an ideal paradigm for the analysis of the determinative events that govern the cell's decision to divide or differentiate. We observed that the mRNA encoding GRIP-1 is expressed in proliferating myoblasts and post-mitotic differentiated myotubes, and that protein levels increase during differentiation. Exogenous/ectopic expression studies with GRIP-1 sense and antisense vectors in myogenic C2C12 cells demonstrated that this SRC is necessary for (1) induction/activation of myogenin, MEF-2, and the crucial cell cycle regulator, p21, and (2) contractile protein expression and myotube formation. Furthermore, we demonstrate that the SRC GRIP-1 coactivates MEF-2C-mediated transcription. GRIP-1 also coactivates the synergistic transactivation of E box-dependent transcription by myogenin and MEF-2C. GST-pulldowns, mammalian two-hybrid analysis, and immunoprecipitation demonstrate that the mechanism involves direct interactions between MEF-2C and GRIP-1 and is associated with the ability of the SRC to interact with the MADS domain of MEF-2C. The HLH region of myogenin mediates the direct interaction of myogenin and GRIP-1. Interestingly, interaction with myogenic factors is mediated by two regions of GRIP-1, an amino-terminal bHLH-PAS region and the carboxy-terminal region between amino acids 1158 and 1423 (which encodes an activation domain, has HAT activity, and interacts with the coactivator-associated arginine methyltransferase). This work demonstrates that GRIP-1 potentiates skeletal muscle differentiation by acting as a critical coactivator for MEF-2C-mediated transactivation and is the first study to ascribe a function to the amino-terminal bHLH-PAS region of SRCs.
Mol Endocrinol. 2001 May;15(5):783-96.
Subcellular localization of the steroid receptor coactivators (SRCs) and MEF2 in muscle and rhabdomyosarcoma cells.
Chen SL, Wang SC, Hosking B, Muscat GE.
University of Queensland Centre for Molecular and Cellular Biology Institute for Molecular Bioscience St. Lucia, 4072 Queensland, Australia.
Skeletal muscle differentiation and the activation of muscle-specific gene expression are dependent on the concerted action of the MyoD family and the MADS protein, MEF2, which function in a cooperative manner. The steroid receptor coactivator SRC-2/GRIP-1/TIF-2, is necessary for skeletal muscle differentiation, and functions as a cofactor for the transcription factor, MEF2. SRC-2 belongs to the SRC family of transcriptional coactivators/cofactors that also includes SRC-1 and SRC-3/RAC-3/ACTR/AIB-1. In this study we demonstrate that SRC-2 is essentially localized in the nucleus of proliferating myoblasts; however, weak (but notable) expression is observed in the cytoplasm. Differentiation induces a predominant localization of SRC-2 to the nucleus; furthermore, the nuclear staining is progressively more localized to dot-like structures or nuclear bodies. MEF2 is primarily expressed in the nucleus, although we observed a mosaic or variegated expression pattern in myoblasts; however, in myotubes all nuclei express MEF2. GRIP-1 and MEF2 are coexpressed in the nucleus during skeletal muscle differentiation, consistent with the direct interaction of these proteins. Rhabdomyosarcoma (RMS) cells derived from malignant skeletal muscle tumors have been proposed to be deficient in cofactors. Alveolar RMS cells very weakly express the steroid receptor coactivator, SRC-2, in a diffuse nucleocytoplasmic staining pattern. MEF2 and the cofactors, SRC-1 and SRC-3 are abundantly expressed in alveolar and embryonal RMS cells; however, the staining is not localized to the nucleus. Furthermore, the subcellular localization and transcriptional activity of MEF2C and a MEF2-dependent reporter are compromised in alveolar RMS cells. In contrast, embryonal RMS cells express SRC-2 in the nucleus, and MEF2 shuttles from the cytoplasm to the nucleus after serum withdrawal. In conclusion, this study suggests that the steroid receptor coactivator SRC-2 and MEF2 are localized to the nucleus during the differentiation process. In contrast, RMS cells display aberrant transcription factor SRC localization and expression, which may underlie certain features of the RMS phenotype.
J Biol Chem. 2005 Feb 11;280(6):4894-905.
Mirk/dyrk1B decreases the nuclear accumulation of class II histone deacetylases during skeletal muscle differentiation.
Deng X, Ewton DZ, Mercer SE, Friedman E.
Department of Pathology, Upstate Medical University, State University of New York, Syracuse, New York 13210, USA.
Mirk/dyrk1B is a member of the dyrk/minibrain family of serine/threonine kinases that mediate the transition from growth to differentiation in lower eukaryotes and mammals. Depletion of endogenous Mirk from C2C12 myoblasts by RNA interference blocks skeletal muscle differentiation (Deng, X., Ewton, D., Pawlikowski, B., Maimone, M., and Friedman, E. (2003) J. Biol. Chem. 278, 41347-41354). We now demonstrate that knockdown of Mirk blocks transcription of the muscle regulatory factor myogenin. Co-expression of Mirk with MEF2C, but not MyoD or Myf5, enhanced activation of the myogenin promoter in a Mirk kinase-dependent manner. Mirk activated MEF2 not through direct phosphorylation of MEF2 but by phosphorylation of its inhibitors, the class II histone deacetylases (HDACs). MEF2 is sequestered by class II HDACs such as HDAC5 and MEF2-interacting transcriptional repressor (MITR). Mirk antagonized the inhibition of MEF2C by MITR, whereas kinase-inactive Mirk was ineffective. Mirk phosphorylates class II HDACs at a conserved site within the nuclear localization region, reducing their nuclear accumulation in a dose-dependent and kinase-dependent manner. Moreover, less mutant MITR phosphomimetic at the Mirk phosphorylation site localized in the nucleus than wild-type MITR. Regulation of class II HDACs occurs by multiple mechanisms. Others have shown that calcium signaling leads to phosphorylation of HDACs at 14-3-3-binding sites, blocking their association with MEF2 within the nucleus. Mirk provides another level of regulation. Mirk is induced within the initial 24 h of myogenic differentiation and enables MEF2 to transcribe the myogenin gene by decreasing the nuclear accumulation of class II HDACs.
dr frankenstein
28/06/2019 2:47 pm
There are far too many steroid co-activators to single out one or two, although it is believed the SRC family acts as a switch between the activating function of the ligand binding pocket and other co-activators.
Keep in mind however, that many co-activators, including SRC, act as co-activators to other nuclear receptors as well, so that simply creating an overexpression of one, may not necessarily prove all that beneficial and could increase problems with estrogen and progesterone receptor related issues.
You seem very interested in nuclear receptor physiology. I can certainly recommend nursa.org as a starting point if you want to get into this more. They have a nice interactive slide show thing as well that details roughly the way nuclear receptors work. The androgen receptor seems to differ somewhat from the other classic nuclear receptors, but it will give you a good idea of how it works nonetheless.
Good things come to those who weight.
The Big Cat is a researcher and theoreticist. His advice must never be taken in the stead of proper advice from a medical professional, it is entirely intended for research purposes.
Topic starter
28/06/2019 3:09 pm
thanks big cat,but i prefer dig of source in source,patiently,but anyway is a good source.
dr frankenstein
Topic starter
28/06/2019 3:30 pm
Nucl Recept Signal. 2006 ;4:e014.
A scoring system for the follow up study of nuclear receptor coactivator complexes.
Han SJ, Jung SY, Malovannaya A, Kim T, Lanz RB, Qin J, O'malley BW.
Department of Molecular and Cellular Biology [SJH, SYJ, AM, TK, RBL, JQ, BWO] and Verna and Mars McLean Department of Biochemistry and Molecular Biology [JQ], Baylor College of Medicine, Houston, Texas, USA.
We have systematically isolated a variety of coactivator complexes from HeLa S3 cells using proteomic approaches. In the present report, we have evaluated twelve coactivator complexes involved in nuclear receptor-dependent gene transcription that have been purified by using an immunoprecipitation method. The twelve purified coactivator complexes are SRC-1, SRC-2, SRC-3, CBP, p300, CAPER, E6-AP, ASC-1, CoREST, CRSP3, CRSP2, and CDK7 containing complexes. We have identified 153 protein components associated with these coactivator complexes using mass spectrometry. In order to systematically characterize the functional roles for these components in nuclear receptor-dependent gene transcription and their investigative potential, we have developed a scoring system. This scoring system is comprised of biological and experimental parameters. The biological evaluation considers aspects such as intrinsic enzymatic activity of a protein component, cellular signaling processes in which protein components may be involved, associations with human disease, specific protein motifs, and the known biological roles of other interacting partners of the identified protein. In the experimental evaluation, we include parameters, such as the availability of research materials for the functional study of the identified protein component; such as full-length cDNA clones, antibodies, and commercially available knock-out embryonic stem (ES) cells. Each scoring parameter has been assigned an arbitrary number of points according to perceived relative importance. On the basis of this scoring system, we prioritized each of the protein components in terms of the likelihood of their importance for coactivator complex networking in nuclear receptor-dependent gene transcription.
Cell. 2006 Aug 25;126(4):789-99.
Anatomical profiling of nuclear receptor expression reveals a hierarchical transcriptional network.
Bookout AL, Jeong Y, Downes M, Yu RT, Evans RM, Mangelsdorf DJ.
Department of Pharmacology, Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, 6001 Forest Park Road, Dallas, 75390, USA.
In multicellular organisms, the ability to regulate reproduction, development, and nutrient utilization coincided with the evolution of nuclear receptors (NRs), transcription factors that utilize lipophilic ligands to mediate their function. Studying the expression profile of NRs offers a simple, powerful way to obtain highly relational information about their physiologic functions as individual proteins and as a superfamily. We surveyed the expression of all 49 mouse NR mRNAs in 39 tissues, representing diverse anatomical systems. The resulting data set uncovers several NR clades whose patterns of expression indicate their ability to coordinate the transcriptional programs necessary to affect distinct physiologic pathways. Remarkably, this regulatory network divides along the following two physiologic paradigms: (1) reproduction, development, and growth and (2) nutrient uptake, metabolism, and excretion. These data reveal a hierarchical transcriptional circuitry that extends beyond individual tissues to form a meganetwork governing physiology on an organismal scale.
dr frankenstein
28/06/2019 3:56 pm
thanks big cat,but i prefer dig of source in source,patiently,but anyway is a good source.
In that case there are two very good review articles you should read, and to the best of my recollection both are free on the pubmed.
Can't remember the exact references but the authors are :
Study 1 : Heinlein and Chang
Study 2 : Smith and O'malley
One study was from 2004 and the other 2002, but can't remember which was which. But they are a good start to understanding AR function and physiology and the role of co-activators.
Good things come to those who weight.
The Big Cat is a researcher and theoreticist. His advice must never be taken in the stead of proper advice from a medical professional, it is entirely intended for research purposes.
Topic starter
28/06/2019 4:25 pm
In that case there are two very good review articles you should read, and to the best of my recollection both are free on the pubmed.Can't remember the exact references but the authors are :
Study 1 : Heinlein and Chang
Study 2 : Smith and O'malleyOne study was from 2004 and the other 2002, but can't remember which was which. But they are a good start to understanding AR function and physiology and the role of co-activators.
it must be, Coregulator function: a key to understanding tissue specificity of selective receptor modulators.
Smith CL, O'Malley BW.
strange thing, you know authors names,but not the paper title.
dr frankenstein
28/06/2019 4:43 pm
I have the papers somewhere, but I didn't feel like looking. Don't see the point either, since both are free on the pubmed so you can get them yourself.
Did you find the other one ? If you can't, try using androgen receptor as a keyword for the title.
I tend to remember author and year of studies I use a lot though, in case I need to do a quick-reference in fast replies
Good things come to those who weight.
The Big Cat is a researcher and theoreticist. His advice must never be taken in the stead of proper advice from a medical professional, it is entirely intended for research purposes.
28/06/2019 5:07 pm
Very good finds.
liftsiron is a fictional character and should be taken as such.
Topic starter
28/06/2019 5:29 pm
I have the papers somewhere, but I didn't feel like looking. Don't see the point either, since both are free on the pubmed so you can get them yourself.Did you find the other one ? If you can't, try using androgen receptor as a keyword for the title.
I tend to remember author and year of studies I use a lot though, in case I need to do a quick-reference in fast replies
i have various from o�malley,i found the other.
Endocr Rev. 2002 Apr;23(2):175-200.
Androgen receptor (AR) coregulators: an overview.
Heinlein CA, Chang C.
George Whipple Laboratory for Cancer Research, Department of Pathology, University of Rochester, New York 14642, USA.
The biological action of androgens is mediated through the androgen receptor (AR). Androgen-bound AR functions as a transcription factor to regulate genes involved in an array of physiological processes, most notably male sexual differentiation and maturation, and the maintenance of spermatogenesis. The transcriptional activity of AR is affected by coregulators that influence a number of functional properties of AR, including ligand selectivity and DNA binding capacity. As the promoter of target genes, coregulators participate in DNA modification, either directly through modification of histones or indirectly by the recruitment of chromatin-modifying complexes, as well as functioning in the recruitment of the basal transcriptional machinery. Aberrant coregulator activity due to mutation or altered expression levels may be a contributing factor in the progression of diseases related to AR activity, such as prostate cancer. AR demonstrates distinct differences in its interaction with coregulators from other steroid receptors due to differences in the functional interaction between AR domains, possibly resulting in alterations in the dynamic interactions between coregulator complexes.
i will buy,the book,
Novel features of transcriptional repression by nuclear receptor corepressor SMRT by Jiujiu Yu
at amazon.com
thanks for the input.
dr frankenstein
28/06/2019 5:52 pm
Not sure if SMRT is of very much use to you if you are researching androgen receptors, there are few ligands that increase SMRT binding. In general SMRT is bound to the AR to repress it in unliganded state, and is released when ligand binds. That goes for most type 1 nuclear receptors. Only some blockers, like RU486, seem to increase AR SMRT binding.
Good things come to those who weight.
The Big Cat is a researcher and theoreticist. His advice must never be taken in the stead of proper advice from a medical professional, it is entirely intended for research purposes.
Topic starter
28/06/2019 6:13 pm
Not sure if SMRT is of very much use to you if you are researching androgen receptors, there are few ligands that increase SMRT binding. In general SMRT is bound to the AR to repress it in unliganded state, and is released when ligand binds. That goes for most type 1 nuclear receptors. Only some blockers, like RU486, seem to increase AR SMRT binding.
to be sincere,AR is part of my interest but, more broadly,gene regulation,gene coregulation,estradiol,thyroid,acth,tsh,leucine,ar
ginine,carbs,proteins,fats etc in the field of metabolic and endocrine physiology with their specific emphases,it is the fourth area in my interests.
in hierarchical order:
#1 ONTOLOGY
#2 METACOSMOLOGY
#3 COGNITIVE PSYCHOBIOLOGY
#4 METABOLIC AND ENDOCRINE PHYSIOLOGY.
Thank you anyway for the attention and courtesy.
dr frankenstein
Topic starter
28/06/2019 6:40 pm
to be sincere,AR is part of my interest but, more broadly,gene regulation,gene coregulation,estradiol,thyroid,acth,tsh,leucine,ar
ginine,carbs,proteins,fats etc in the field of metabolic and endocrine physiology with their specific emphases,.................
articles like
Cell, Vol 126, 929-940, 08 September 2006
The HAMP Domain Structure Implies Helix Rotation in Transmembrane Signaling.
Michael Hulko,1 Franziska Berndt,2 Markus Gruber,1 J�rgen U. Linder,2 Vincent Truffault,1 Anita Schultz,2 J�rg Martin,1 Joachim E. Schultz,2 Andrei N. Lupas,1, and Murray Coles1
1 Department of Protein Evolution, Max-Planck-Institute for Developmental Biology, 72076 T�bingen, Germany
2 Department of Pharmaceutical Biochemistry, School of Pharmacy, T�bingen University, 72076 T�bingen, Germany
HAMP domains connect extracellular sensory with intracellular signaling domains in over 7500 proteins, including histidine kinases, adenylyl cyclases, chemotaxis receptors, and phosphatases. The solution structure of an archaeal HAMP domain shows a homodimeric, four-helical, parallel coiled coil with unusual interhelical packing, related to the canonical packing by rotation of the helices. This suggests a model for the mechanism of signal transduction, in which HAMP alternates between the observed conformation and a canonical coiled coil. We explored this mechanism in vitro and in vivo using HAMP domain fusions with a mycobacterial adenylyl cyclase and an E. coli chemotaxis receptor. Structural and functional studies show that the equilibrium between the two forms is dependent on the side-chain size of residue 291, which is alanine in the wild-type protein.
Based on the interdigitation of the side chains in this structure, the authors propose a cogwheel model for signal transduction, which involves the concerted rotation of the helices in a plane perpendicular to the membrane
dr frankenstein