Aurora Kinase A Regulates Cell Transitions in Glucocorticoid-Induced Bone Loss.

Glucocorticoid-induced bone loss is a severe and toxic effect of long-term therapy with glucocorticoids, which are currently prescribed for millions of people worldwide. Previous studies have uncovered that glucocorticoids reciprocally converted osteoblast lineage cells into endothelial-like cells to cause bone loss and showed that the modulations of Foxc2 and Osterix were the causative factors that drove this harmful transition of osteoblast lineage cells. Here, we find that the inhibition of aurora kinase A halts this transition and prevents glucocorticoid-induced bone loss. We find that aurora A interacts with the glucocorticoid receptor and show that this interaction is required for glucocorticoids to modulate Foxc2 and Osterix. Together, we identify a new potential approach to counteracting unwanted transitions of osteoblast lineage cells in glucocorticoid treatment and may provide a novel strategy for ameliorating glucocorticoid-induced bone loss.

Single-Cell RNA-Seq Identifies Dynamic Cardiac Transition Program from ADCs Induced by Leukemia Inhibitory Factor.

Adipose-derived cells (ADCs) from white adipose tissue are promising stem cell candidates because of their large regenerative reserves and the potential for cardiac regeneration. However, given the heterogeneity of ADC and its unsolved mechanisms of cardiac acquisition, ADC-cardiac transition efficiency remains low. In this study, we explored the heterogeneity of ADCs and the cellular kinetics of 39,432 single-cell transcriptomes along the leukemia inhibitory factor (LIF)-induced ADC-cardiac transition. We identified distinct ADC subpopulations that reacted differentially to LIF when entering the cardiomyogenic program, further demonstrating that ADC-myogenesis is time-dependent and initiates from transient changes in nuclear factor erythroid 2-related factor 2 (Nrf2) signaling. At later stages, pseudotime analysis of ADCs navigated a trajectory with 2 branches corresponding to activated myofibroblast or cardiomyocyte-like cells. Our findings offer a high-resolution dissection of ADC heterogeneity and cell fate during ADC-cardiac transition, thus providing new insights into potential cardiac stem cells.

Resistin and risks of incident heart failure subtypes and cardiac fibrosis: the Multi-Ethnic Study of Atherosclerosis.

AIMS: Resistin is a circulating inflammatory biomarker that is associated with cardiovascular disease. We investigated the associations of resistin and incident heart failure (HF) and its subtypes, as well as specific measures of subclinical HF (myocardial fibrosis and relevant biomarkers). METHODS: We analysed data from 1968 participants in the Multi-Ethnic Study of Atherosclerosis with measurements of plasma resistin levels at clinic visits from 2002 to 2005. Participants were subsequently followed for a median of 10.5 years for HF events. The associations between resistin levels and incident HF, HF with reduced ejection fraction (HFrEF), and HF with preserved ejection fraction (HFpEF) were examined using multivariable Cox proportional hazards models. Linear regression models assessed the associations between resistin levels and myocardial fibrosis from cardiac magnetic resonance imaging, as well as hs-cTnT and NT-proBNP. RESULTS: The mean age of the cohort was 64.7 years, and 50.0% were female. Seventy-four participants (4%) developed incident HF during follow-up. In a Cox proportional hazards model adjusted for age, gender, education level, race/ethnicity, and traditional risk factors, higher resistin levels were significantly associated with incident HF (HR 1.44, CI 1.18-1.75, P = 0.001) and HFrEF (HR 1.47, CI 1.07-2.02, P = 0.016), but not with HFpEF (HR 1.25, CI 0.89-1.75, P = 0.195). Resistin levels showed no significant associations with myocardial fibrosis, NT-proBNP, or hs-cTnT levels. CONCLUSIONS: In a multi-ethnic cohort free of cardiovascular disease at baseline, elevated resistin levels were associated with incident HF, more prominently with incident HFrEF than HFpEF, but not with subclinical myocardial fibrosis or biomarkers of HF.

NAADP-binding proteins find their identity.

Nicotinic acid adenine dinucleotide phosphate (NAADP) is a second messenger that releases Ca2+ from endosomes and lysosomes by activating ion channels called two-pore channels (TPCs). However, no NAADP-binding site has been identified on TPCs. Rather, NAADP activates TPCs indirectly by engaging NAADP-binding proteins (NAADP-BPs) that form part of the TPC complex. After a decade of searching, two different NAADP-BPs were recently identified: Jupiter microtubule associated homolog 2 (JPT2) and like-Sm protein 12 (LSM12). These discoveries bridge the gap between NAADP generation and NAADP activation of TPCs, providing new opportunity to understand and manipulate the NAADP-signaling pathway. The unmasking of these NAADP-BPs will catalyze future studies to define the molecular choreography of NAADP action.

Intact parathyroid hormone levels and primary hyperparathyroidism.

OBJECTIVE: The aim of this article is to compare clinical characteristics and lab values for metabolic syndrome between primary hyperparathyroidism (PHPT) patients with different levels of serum intact parathyroid hormone (iPTH) and to determine correlation between different clinical characteristics among PHPT patients Methods: We reviewed charts of 212 PHPT patients in this retrospective study. Patients were divided into two groups according to their initial serum iPTH levels. Student's t-tests were used to compare the two groups for differences in clinical characteristics and laboratory values. Pearson's correlation coefficients were used to assess associations. RESULTS: Of the 212 PHPT patients, 100 were classified as m-iPTH group (serum iPTH < 140 pg/mL), whereas 112 patients were defined as h-iPTH group (serum iPTH ≥ 140 pg/mL). The h-iPTH patients were younger, had higher serum calcium and alkaline phosphatase levels, but exhibited lower 25(OH)-vitamin D and HDL levels, when compared with those of m-iPTH patients. Adenoma weights in the h-iPTH group tended to be higher than that in the m-iPTH group. Furthermore, association studies revealed that the iPTH level was positively correlated with adenoma weight and serum calcium and triglyceride (TG) levels but negatively correlated with HDL level. CONCLUSION: Our study supports the hypothesis that iPTH level is associated with TG and HDL levels and should be a factor to consider in the management of PHPT patients.

IMPACT OF ETHNIC BACKGROUND ON CLINICAL CHARACTERISTICS AND CARDIOVASCULAR RISK FACTORS AMONG PATIENTS WITH PRIMARY HYPERPARATHYROIDISM.

OBJECTIVE: To compare initial laboratory values and cardiovascular risk factors (CRF) among patients with primary hyperparathyroidism (PHPT) of different ethnic backgrounds. METHODS: In this retrospective study, we reviewed 500 charts of PHPT patients who presented at Robert Wood Johnson University Hospital from January 2000 to December 2013. Among these patients were 46 African Americans (AA), 31 Asians (A), 19 Hispanics (H), and 404 Caucasians (C). The following characteristics were compared between the groups: age; body mass index (BMI); levels of serum calcium, intact parathyroid hormone (iPTH), 25-OH vitamin D, and 24-hour urine calcium; and parathyroid adenoma weight. Presence of CRF including BMI, diabetes mellitus, hypertension, and hyperlipidemia were also recorded for comparison. Associations of adenoma weight and several other parameters were also assessed. RESULTS: Among different ethnic groups, AA patients with PHPT had higher iPTH levels compared to the A and C groups (P<.05), while 25-OHD levels were lower in the AA compared to the A and C groups (P<.05). Adenoma weight was significantly greater in AA than in C and A PHPT patients (P<.01). Adenoma weight was positively correlated with iPTH levels (r = 0.493, P <.001) and serum calcium levels (r = 0.255, P<.01). The group BMIs were C: 29.5 ± 6.9, AA: 33.8 ± 10, A: 24.7 ± 3.3, and H: 30.2 ± 6.6. AA patients had a lower rate of renal stones (9%) compared to other groups (21-29%, P<.05). CONCLUSION: The results of our study indicate that AA patients with PHPT presented with a more severe PHPT profile but had lower 24-hour urine calcium and fewer renal stones. AA patients with PHPT also had higher prevalence of CRF when compared to A and C.

G protein-coupled receptor kinase-5 attenuates atherosclerosis by regulating receptor tyrosine kinases and 7-transmembrane receptors.

OBJECTIVE: G protein-coupled receptor kinase-5 (GRK5) is a widely expressed Ser/Thr kinase that regulates several atherogenic receptors and may activate or inhibit nuclear factor-κB (NF-κB). This study sought to determine whether and by what mechanisms GRK5 affects atherosclerosis. METHODS AND RESULTS: Grk5(-/-)/Apoe(-/-) mice developed 50% greater aortic atherosclerosis than Apoe(-/-) mice and demonstrated greater proliferation of macrophages and smooth muscle cells (SMCs) in atherosclerotic lesions. In Apoe(-/-) mice, carotid interposition grafts from Grk5(-/-) mice demonstrated greater upregulation of cell adhesion molecules than grafts from wild-type mice and, subsequently, more atherosclerosis. By comparing Grk5(-/-) with wild-type cells, we found that GRK5 desensitized 2 key atherogenic receptor tyrosine kinases: the platelet-derived growth factor receptor-ß in SMCs, by augmenting ubiquitination/degradation; and the colony-stimulating factor-1 receptor (CSF-1R) in macrophages, by reducing CSF-1-induced tyrosyl phosphorylation. GRK5 activity in monocytes also reduced migration promoted by the 7-transmembrane receptor for monocyte chemoattractant protein-1 CC chemokine receptor-2. Whereas GRK5 diminished NF-κB-dependent gene expression in SMCs and endothelial cells, it had no effect on NF-κB activity in macrophages. CONCLUSIONS: GRK5 attenuates atherosclerosis through multiple cell type-specific mechanisms, including reduction of SMC and endothelial cell NF-κB activity and desensitization of receptor-specific signaling through the monocyte CC chemokine receptor-2, macrophage CSF-1R, and the SMC platelet-derived growth factor receptor-ß.

Molecular evolution and functional divergence of the Ca(2+) sensor protein in store-operated Ca(2+) entry: stromal interaction molecule.

Receptor-mediated Ca(2+) signaling in many non-excitable cells initially induces Ca(2+) release from intracellular Ca(2+) stores, followed by Ca(2+) influx across the plasma membrane. Recent findings have suggested that stromal interaction molecules (STIMs) function as the Ca(2+) sensor to detect changes of Ca(2+) content in the intracellular Ca(2+) stores. Human STIMs and invertebrate STIM share several functionally important protein domains, but diverge significantly in the C-terminus. To better understand the evolutionary significance of STIM activity, phylogenetic analysis of the STIM protein family was conducted after extensive database searching. Results from phylogeny and sequence analysis revealed early adaptation of the C-terminal divergent domains in Urochordata, before the expansion of STIMs in Vertebrata. STIMs were subsequently subjected to one round of gene duplication as early as in the Euteleostomi lineage in vertebrates, with a second round of fish-specific gene duplication. After duplication, STIM-1 and STIM-2 molecules appeared to have undergone purifying selection indicating strong evolutionary constraints within each group. Furthermore, sequence analysis of the EF-hand Ca(2+) binding domain and the SAM domain, together with functional divergence studies, identified critical regions/residues likely underlying functional changes, and provided evidence for the hypothesis that STIM-1 and STIM-2 might have developed distinct functional properties after duplication.

A novel topology and redox regulation of the rat brain K+-dependent Na+/Ca2+ exchanger, NCKX2.

In this study we have examined the roles of endogenous cysteine residues in the rat brain K(+)-dependent Na(+)/Ca(2+) exchanger protein, NCKX2, by site-directed mutagenesis. We found that mutation of Cys-614 or Cys-666 to Ala inhibited expression of the exchanger protein in HEK-293 cells, but not in an in vitro translation system. We speculated that Cys-614 and Cys-666 might form an extracellular disulfide bond that stabilized protein structure. Such an arrangement would place the C terminus of the exchanger outside the cell, contrary to the original topological model. This hypothesis was tested by adding a hemagglutinin A epitope to the C terminus of the protein. The hemagglutinin A epitope could be recognized with a specific antibody without permeabilization of the cell membrane, supporting an extracellular location for the C terminus. Additionally, the exchanger molecule could be labeled with biotin maleimide only following extracellular application of beta-mercaptoethanol. Surprisingly, mutation of Cys-395, located in the large intracellular loop, to Ala, prevented reduction-dependent labeling of the protein. The activity of wild-type exchanger, but not the Cys-395 --> Ala mutant, was stimulated after application of beta-mercaptoethanol. Co-immunoprecipitation experiments demonstrated self-association between wild-type and FLAG-tagged exchanger proteins that could not be inhibited by Cys-395 --> Ala mutation. These results suggest that NCKX2 associates as a dimer, an interaction that does not require, but may be stabilized by, a disulfide linkage through Cys-395. This linkage, perhaps by limiting protein mobility along the dimer interface, reduces the transport activity of NCKX2.