scholarly journals The BRCA1/BARD1 ubiquitin ligase and its substrates

2021 ◽  
Vol 478 (18) ◽  
pp. 3467-3483
Author(s):  
Samuel R. Witus ◽  
Mikaela D. Stewart ◽  
Rachel E. Klevit
Keyword(s):  
Estrogen Receptor Α ◽  
Cancer Type ◽  
Experimental Systems ◽  
Road Map ◽  
Enzymatic Function ◽  
Experimental Approaches ◽  
Cycle Regulation ◽  
Substrate Proteins

Mutations in breast cancer type 1 susceptibility protein (BRCA1) and its heterodimeric binding partner BARD1 confer a high risk for the development of breast and ovarian cancers. The sole enzymatic function of the BRCA1/BARD1 complex is as a RING-type E3 ubiquitin (Ub) ligase, leading to the deposition of Ub signals onto a variety of substrate proteins. Distinct types of Ub signals deposited by BRCA1/BARD1 (i.e. degradative vs. non-degradative; mono-Ub vs. poly-Ub chains) on substrate proteins mediate aspects of its function in DNA double-stranded break repair, cell-cycle regulation, and transcriptional regulation. While cancer-predisposing mutations in both subunits lead to the inactivation of BRCA1/BARD1 ligase activity, controversy remains as to whether its Ub ligase activity directly inhibits tumorigenesis. Investigation of BRCA1/BARD1 substrates using rigorous, well-validated mutants and experimental systems will ultimately clarify the role of its ligase activity in cancer and possibly establish prognostic and diagnostic metrics for patients with mutations. In this review, we discuss the Ub ligase function of BRCA1/BARD1, highlighting experimental approaches, mechanistic considerations, and reagents that are useful in the study of substrate ubiquitylation. We also discuss the current understanding of two well-established BRCA1/BARD1 substrates (nucleosomal H2A and estrogen receptor α) and several recently discovered substrates (p50, NF2, Oct1, and LARP7). Lessons from the current body of work should provide a road map to researchers examining novel substrates and biological functions attributed to BRCA1/BARD1 Ub ligase activity.

The angiotensin II type 2 receptor: an enigma with multiple variations

2000 ◽  
Vol 278 (3) ◽  
pp. E357-E374 ◽  
Author(s):  
Stefan Gallinat ◽  
Silke Busche ◽  
Mohan K. Raizada ◽  
Colin Sumners
Keyword(s):  
Angiotensin Ii ◽  
Singular Function ◽  
Ang Ii ◽  
Experimental Approaches ◽  
Number Of Publications ◽  
Cardiovascular Functions ◽  
Made In

Since it was discovered ten years ago, the angiotensin II (ANG II) type 2 (AT2) receptor has been an enigma. This receptor binds ANG II with a high affinity but is not responsible for mediating any of the classical physiological actions of this peptide, all of which involve the ANG II type 1 (AT1) receptor. Furthermore, the AT2 receptor exhibits dramatic differences in biochemical and functional properties and in patterns of expression compared with the AT1 receptor. During the past decade, much information has been gathered about the AT2 receptor, and the steadily increasing number of publications indicates a growing interest in this new and independent area of research. A number of studies suggest a role of AT2 receptors in brain, renal, and cardiovascular functions and in the processes of apoptosis and tissue regeneration. Despite these advances, nothing stands out as the major singular function of these receptors. The study of AT2 receptors has reached a crossroads, and innovative approaches must be considered so that unifying mechanisms as to the function of these unique receptors can be put forward. In this review we will discuss the advances that have been made in understanding the biology of the AT2receptor. Furthermore, we will consider how these discoveries, along with newer experimental approaches, may eventually lead to the elusive physiological and pathophysiological functions of these receptors.

scholarly journals The Role of the Active Site Cysteine in Catalysis by Type 1 Iodothyronine Deiodinase*

Endocrinology ◽  
1997 ◽  
Vol 138 (12) ◽  
pp. 5452-5458 ◽  
Author(s):  
Ben C. Sun ◽  
John W. Harney ◽  
Marla J. Berry ◽  
P. Reed Larsen
Keyword(s):  
Active Site ◽  
Outer Ring ◽  
Substrate Affinity ◽  
Maximal Velocity ◽  
Wild Type ◽  
Iodothyronine Deiodinase ◽  
Active Site Cysteine ◽  
Enzymatic Function

Abstract Type 1 iodothyronine deiodinase (deiodinase 1) is a selenoenzyme that converts the prohormone T4 to the active thyroid hormone T3 by outer ring deiodination or to the inactive metabolite rT3 by inner ring deiodination. Although selenocysteine has been demonstrated to be essential for the biochemical profile of deiodinase 1, the role of a highly conserved, active site cysteine (C124 in rat deiodinase 1) has not been defined. The present studies examined the effects of a Cys124Ala mutation on rat deiodinase 1 enzymatic function and substrate affinity. At a constant 10-mm concentration of dithiothreitol (DTT), the C124A mutant demonstrated a 2-fold lower apparent maximal velocity (Vmax) and Km for rT3 (KmrT3) than the wild type for outer ring deiodination, whereas the Vmax/Km ratio was unchanged. Similarly, the apparent Vmax and KmT3 sulfate for inner ring deiodination were 2-fold lower in the C124A mutant relative to those in the wild type, with no change in the Vmax/Km ratio. The C124A mutant exhibited ping-pong kinetics in the presence of DTT, and substitution of the active site cysteine increased the KmDTT by 14-fold relative to that of the wild-type enzyme, with no significant effects on KmrT3 or Vmax. The C124A mutant was inhibited by propylthiouracil in an uncompetitive fashion and exhibited a 2-fold increase in Kipropylthiouracil compared with that of the wild type. KmrT3 was also reduced for the C124A mutant when 5 mm reduced glutathione, a potential physiological monothiol cosubstrate, was used in outer ring deiodination assays. These results demonstrate that thiol cosubstrate interactions with C124 in type 1 deiodinase play an important role in enhancing catalytic efficiency for both outer and inner ring deiodination.

Role of herpes simplex virus type 1 (HSV-1) in the pathogenesis of peptic ulcer disease

2001 ◽  
Vol 120 (5) ◽  
pp. A136-A137
Author(s):  
K TSAMAKIDES ◽  
E PANOTOPOULOU ◽  
D DIMITROULOPOULOS ◽  
M CHRISTOPOULO ◽  
D XINOPOULOS ◽  
...  
Keyword(s):  
Peptic Ulcer ◽  
Herpes Simplex Virus ◽  
Herpes Simplex ◽  
Peptic Ulcer Disease ◽  
Virus Type ◽  
Herpes Simplex Virus Type ◽  
Ulcer Disease ◽  
Simplex Virus

The Role of Secrecy and Disclosure in Type 1 Diabetes Adherence and Glycemic Control

2013 ◽  
Author(s):  
P. Osborn ◽  
C. A. Berg ◽  
A. E. Hughes ◽  
P. Pham ◽  
D. J. Wiebe
Keyword(s):  
Type 1 Diabetes ◽  
Glycemic Control

Dissecting the role of Corticotropin-releasing hormone receptor type 1 in Alzheimer's Disease

2011 ◽  
Vol 44 (06) ◽  
Author(s):  
K Lerche ◽  
M Willem ◽  
K Kleinknecht ◽  
C Romberg ◽  
U Konietzko ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Hormone Receptor ◽  
Receptor Type ◽  
Corticotropin Releasing Hormone ◽  
Releasing Hormone

The role of hepatic 11[b]-hydroxysteroid dehydrogenase type 1 in cholesterol homeostasis

2013 ◽  
pp. 1-1
Author(s):  
Kajal Manwani ◽  
Tak Y Man ◽  
Christopher J Kenyon ◽  
Ruth Andrew ◽  
Karen E Chapman ◽  
...  
Keyword(s):  
Hydroxysteroid Dehydrogenase ◽  
Cholesterol Homeostasis

Membrane estrogen receptor α is essential for estrogen signaling in the male skeleton

2018 ◽  
Vol 239 (3) ◽  
pp. 303-312 ◽  
Author(s):  
H H Farman ◽  
K L Gustafsson ◽  
P Henning ◽  
L Grahnemo ◽  
V Lionikaite ◽  
...  
Keyword(s):  
Estrogen Receptor ◽  
Estrogen Receptor Α ◽  
Estrogen Signaling ◽  
Areal Bone Mineral Density ◽  
Male Mice ◽  
Mineral Density ◽  
Intact Male ◽  
Trabecular Thickness ◽  
Total Body

The importance of estrogen receptor α (ERα) for the regulation of bone mass in males is well established. ERα mediates estrogenic effects both via nuclear and membrane-initiated ERα (mERα) signaling. The role of mERα signaling for the effects of estrogen on bone in male mice is unknown. To investigate the role of mERα signaling, we have used mice (Nuclear-Only-ER; NOER) with a point mutation (C451A), which results in inhibited trafficking of ERα to the plasma membrane. Gonadal-intact male NOER mice had a significantly decreased total body areal bone mineral density (aBMD) compared to WT littermates at 3, 6 and 9 months of age as measured by dual-energy X-ray absorptiometry (DEXA). High-resolution microcomputed tomography (µCT) analysis of tibia in 3-month-old males demonstrated a decrease in cortical and trabecular thickness in NOER mice compared to WT littermates. As expected, estradiol (E2) treatment of orchidectomized (ORX) WT mice increased total body aBMD, trabecular BV/TV and cortical thickness in tibia compared to placebo treatment. E2 treatment increased these skeletal parameters also in ORX NOER mice. However, the estrogenic responses were significantly decreased in ORX NOER mice compared with ORX WT mice. In conclusion, mERα is essential for normal estrogen signaling in both trabecular and cortical bone in male mice. Increased knowledge of estrogen signaling mechanisms in the regulation of the male skeleton may aid in the development of new treatment options for male osteoporosis.

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