Exploring epigenetic strategies for the treatment of osteoporosis

The worldwide trend toward an aging population has resulted in a higher incidence of chronic conditions, such as osteoporosis. Osteoporosis, a prevalent skeletal disorder characterized by decreased bone mass and increased fracture risk, encompasses primary and secondary forms, each with distinct etiologies. Mechanistically, osteoporosis involves an imbalance between bone resorption by osteoclasts and bone formation by osteoblasts. Current pharmacological interventions for osteoporosis, such as bisphosphonates, denosumab, and teriparatide, aim to modulate bone turnover and preserve bone density. Hormone replacement therapy and lifestyle modifications are also recommended to manage the condition. While current medications offer therapeutic options, they are not devoid of limitations. Recent studies have highlighted the importance of epigenetic mechanisms, including DNA methylation and histone modifications, in regulating gene expression during bone remodeling. The use of epigenetic drugs, or epidrugs, to target these mechanisms offers a promising avenue for therapeutic intervention in osteoporosis. In this review, we comprehensively examine the recent advancements in the application of epidrugs for treating osteoporosis.

Dimethyl alpha-ketoglutarate inhibits proliferation in diffuse intrinsic pontine glioma by reprogramming epigenetic and transcriptional networks

Diffuse intrinsic pontine glioma (DIPG) is a highly aggressive pediatric brain tumor with limited therapeutic options. Here, we investigated the potential of dimethyl alpha-ketoglutarate (DMKG) as an anti-proliferative agent against DIPG and unraveled its underlying molecular mechanisms. DMKG exhibited robust inhibition of DIPG cell proliferation, colony formation, and neurosphere growth. Transcriptomic analysis revealed substantial alterations in gene expression, with upregulated genes enriched in hypoxia-related pathways and downregulated genes associated with cell division and the mitotic cell cycle. Notably, DMKG induced G1/S phase cell cycle arrest and downregulated histone H3 lysine 27 acetylation (H3K27ac) without affecting H3 methylation levels. The inhibition of AKT and ERK signaling pathways by DMKG coincided with decreased expression of the CBP/p300 coactivator. Importantly, we identified the c-MYC-p300/ATF1-p300 axis as a key mediator of DMKG's effects, demonstrating reduced binding to target gene promoters and decreased H3K27ac levels. Depletion of c-MYC or ATF1 effectively inhibited DIPG cell growth. These findings highlight the potent anti-proliferative properties of DMKG, its impact on epigenetic modifications, and the involvement of the c-MYC-p300/ATF1-p300 axis in DIPG, shedding light on potential therapeutic strategies for this devastating disease.

TMBIM6 deficiency leads to bone loss by accelerating osteoclastogenesis

TMBIM6 is an endoplasmic reticulum (ER) protein that modulates various physiological and pathological processes, including metabolism and cancer. However, its involvement in bone remodeling has not been investigated. In this study, we demonstrate that TMBIM6 serves as a crucial negative regulator of osteoclast differentiation, a process essential for bone remodeling. Our investigation of Tmbim6-knockout mice revealed an osteoporotic phenotype, and knockdown of Tmbim6 inhibited the formation of multinucleated tartrate-resistant acid phosphatase-positive cells, which are characteristic of osteoclasts. Transcriptome and immunoblot analyses uncovered that TMBIM6 exerts its inhibitory effect on osteoclastogenesis by scavenging reactive oxygen species and preventing p65 nuclear localization. Additionally, TMBIM6 depletion was found to promote p65 localization to osteoclast-related gene promoters. Notably, treatment with N-acetyl cysteine, an antioxidant, impeded the osteoclastogenesis induced by TMBIM6-depleted cells, supporting the role of TMBIM6 in redox regulation. Furthermore, we discovered that TMBIM6 controls redox regulation via NRF2 signaling pathways. Our findings establish TMBIM6 as a critical regulator of osteoclastogenesis and suggest its potential as a therapeutic target for the treatment of osteoporosis.

Gene regulation by histone-modifying enzymes under hypoxic conditions: a focus on histone methylation and acetylation

Oxygen, which is necessary for sustaining energy metabolism, is consumed in many biochemical reactions in eukaryotes. When the oxygen supply is insufficient for maintaining multiple homeostatic states at the cellular level, cells are subjected to hypoxic stress. Hypoxia induces adaptive cellular responses mainly through hypoxia-inducible factors (HIFs), which are stabilized and modulate the transcription of various hypoxia-related genes. In addition, many epigenetic regulators, such as DNA methylation, histone modification, histone variants, and adenosine triphosphate-dependent chromatin remodeling factors, play key roles in gene expression. In particular, hypoxic stress influences the activity and gene expression of histone-modifying enzymes, which controls the posttranslational modification of HIFs and histones. This review covers how histone methylation and histone acetylation enzymes modify histone and nonhistone proteins under hypoxic conditions and surveys the impact of epigenetic modifications on gene expression. In addition, future directions in this area are discussed.

New sequencing technologies are revealing how cells respond to hypoxia, insufficient oxygen, by managing gene activation. In multicellular organisms, gene activation is managed by how tightly a section of DNA is wound around proteins called histones; genes in tightly packed regions are inaccessible and inactive, whereas those in looser regions can be activated. Kyunghwan Kim, Sun-Ju Yi, and co-workers at Chungbuk National University in South Korea have reviewed recent data on how cells regulate gene activity under hypoxic conditions. Advances in sequencing technology have allowed genome-wide studies of how hypoxia affects DNA structure and gene activation, revealing that gene-specific modifications may be more important than genome-wide modifications. Hypoxia is implicated in several diseases, such as cancer and chronic metabolic diseases, and a better understanding of how it affects gene activation may help identify new treatments for hypoxia-related diseases.

The role of histone modifications: from neurodevelopment to neurodiseases

Epigenetic regulatory mechanisms, including DNA methylation, histone modification, chromatin remodeling, and microRNA expression, play critical roles in cell differentiation and organ development through spatial and temporal gene regulation. Neurogenesis is a sophisticated and complex process by which neural stem cells differentiate into specialized brain cell types at specific times and regions of the brain. A growing body of evidence suggests that epigenetic mechanisms, such as histone modifications, allow the fine-tuning and coordination of spatiotemporal gene expressions during neurogenesis. Aberrant histone modifications contribute to the development of neurodegenerative and neuropsychiatric diseases. Herein, recent progress in understanding histone modifications in regulating embryonic and adult neurogenesis is comprehensively reviewed. The histone modifications implicated in neurodegenerative and neuropsychiatric diseases are also covered, and future directions in this area are provided.

[Controversy and progress on whether to retain left colonic artery in radical resection of rectal cancer]

Japanese Society for Cancer of the Colon and Rectum (JSCCR) guideline 2019 recommended that lymph node dissection for advanced rectal cancer should include the lymphatic adipose tissue at the root of the inferior mesenteric vessels, but the ligation site of the inferior mesenteric artery (IMA) was not determined, and the NCCN guideline did not indicate clearly whether to retain the left colonic artery (LCA). Controversy over whether to retain LCA is no more than whether it can reduce the incidence of anastomotic complications or postoperative functional damage without affecting the patients' oncological outcome. Focusing on the above problems, this paper reviews the latest research progress. In conclusion, it is believed that the advantages of retaining LCA are supported by most studies, which can improve the blood supply of the proximal anastomosis, and technically can achieve the same range of lymph node dissection as IMA high ligation. However, whether it affects the survival of patients, reduces the incidence of anastomotic leakage, and improves the quality of life of patients, more high-quality evidence-based medical evidence is still needed.

The KDM4B-CCAR1-MED1 axis is a critical regulator of osteoclast differentiation and bone homeostasis

Bone undergoes a constant and continuous remodeling process that is tightly regulated by the coordinated and sequential actions of bone-resorbing osteoclasts and bone-forming osteoblasts. Recent studies have shown that histone demethylases are implicated in osteoblastogenesis; however, little is known about the role of histone demethylases in osteoclast formation. Here, we identified KDM4B as an epigenetic regulator of osteoclast differentiation. Knockdown of KDM4B significantly blocked the formation of tartrate-resistant acid phosphatase-positive multinucleated cells. Mice with myeloid-specific conditional knockout of KDM4B showed an osteopetrotic phenotype due to osteoclast deficiency. Biochemical analysis revealed that KDM4B physically and functionally associates with CCAR1 and MED1 in a complex. Using genome-wide chromatin immunoprecipitation (ChIP)-sequencing, we revealed that the KDM4B–CCAR1–MED1 complex is localized to the promoters of several osteoclast-related genes upon receptor activator of NF-κB ligand stimulation. We demonstrated that the KDM4B–CCAR1–MED1 signaling axis induces changes in chromatin structure (euchromatinization) near the promoters of osteoclast-related genes through H3K9 demethylation, leading to NF-κB p65 recruitment via a direct interaction between KDM4B and p65. Finally, small molecule inhibition of KDM4B activity impeded bone loss in an ovariectomized mouse model. Taken together, our findings establish KDM4B as a critical regulator of osteoclastogenesis, providing a potential therapeutic target for osteoporosis.

Enhanced wound healing using a 3D printed VEGF-mimicking peptide incorporated hydrogel patch in a pig model

There is a need for effective wound healing through rapid wound closure, reduction of scar formation, and acceleration of angiogenesis. Hydrogel is widely used in tissue engineering, but it is not an ideal solution because of its low vascularization capability and poor mechanical properties. In this study, gelatin methacrylate (GelMA) was tested as a viable option with tunable physical properties. GelMA hydrogel incorporating a vascular endothelial growth factor (VEGF) mimicking peptide was successfully printed using a three-dimensional (3D) bio-printer owing to the shear-thinning properties of hydrogel inks. The 3D structure of the hydrogel patch had high porosity and water absorption properties. Furthermore, the bioactive characterization was confirmed by cell culture with mouse fibroblasts cell lines (NIH 3T3) and human umbilical vein endothelial cells. VEGF peptide, which is slowly released from hydrogel patches, can promote cell viability, proliferation, and tubular structure formation. In addition, a pig skin wound model was used to evaluate the wound-healing efficacy of GelMA-VEGF hydrogel patches; the results suggest that the GelMA-VEGF hydrogel patch can be used for wound dressing.

Environment-mediated drug resistance in Bcr/Abl-positive acute lymphoblastic leukemia

Although cure rates for acute lymphoblastic leukemia (ALL) have increased, development of resistance to drugs and patient relapse are common. The environment in which the leukemia cells are present during the drug treatment is known to provide significant survival benefit. Here, we have modeled this process by culturing murine Bcr/Abl-positive acute lymphoblastic leukemia cells in the presence of stroma while treating them with a moderate dose of two unrelated drugs, the farnesyltransferase inhibitor lonafarnib and the tyrosine kinase inhibitor nilotinib. This results in an initial large reduction in cell viability of the culture and inhibition of cell proliferation. However, after a number of days, cell death ceases and the culture becomes drug-tolerant, enabling cell division to resume. Using gene expression profiling, we found that the development of drug resistance was accompanied by massive transcriptional upregulation of genes that are associated with general inflammatory responses such as the metalloproteinase MMP9. MMP9 protein levels and enzymatic activity were also increased in ALL cells that had become nilotinib-tolerant. Activation of p38, Akt and Erk correlated with the development of environment-mediated drug resistance (EMDR), and inhibitors of Akt and Erk in combination with nilotinib reduced the ability of the cells to develop resistance. However, inhibition of p38 promoted increased resistance to nilotinib. We conclude that development of EMDR by ALL cells involves changes in numerous intracellular pathways. Development of tolerance to drugs such as nilotinib may therefore be circumvented by simultaneous treatment with other drugs having divergent targets.

Transcriptome profiling of olive flounder responses under acute and chronic heat stress

BACKGROUND

The olive flounder (Paralichthys olivaceus) is a saltwater fish, which is valuable to the economy. The olive flounder strives to adapt to environmental stressors through physiological, biochemical, and transcriptional responses. The rise in water temperature threatens the growth, development, reproduction, and survival of olive flounder. Each organ in the olive flounder can differentially respond to heat stress.

OBJECTIVES

The purpose of this study is to investigate organ-specific transcriptional changes in olive flounder tissues during heat stress.

METHODS

In this study, transcriptome dynamics of the gill, liver, and muscle of olive flounder to acute or chronic heat stress were investigated.

RESULTS

Principal component analysis plotting revealed that the transcriptome of each organ is quite separated. K-means clustering, gene ontology, and Kyoto Encyclopedia of Genes and Genomes pathway analysis showed the differential transcriptome responses of each organ to heat stress. Heat stress commonly affects the pathways involved in the correct protein folding, DNA repair, and cell cycle.

CONCLUSION

Our results may provide a valuable molecular basis of heat acclimation in fishes.

New Insights into the Role of Histone Changes in Aging

Aging is the progressive decline or loss of function at the cellular, tissue, and organismal levels that ultimately leads to death. A number of external and internal factors, including diet, exercise, metabolic dysfunction, genome instability, and epigenetic imbalance, affect the lifespan of an organism. These aging factors regulate transcriptome changes related to the aging process through chromatin remodeling. Many epigenetic regulators, such as histone modification, histone variants, and ATP-dependent chromatin remodeling factors, play roles in chromatin reorganization. The key to understanding the role of gene regulatory networks in aging lies in characterizing the epigenetic regulators responsible for reorganizing and potentiating particular chromatin structures. This review covers epigenetic studies on aging, discusses the impact of epigenetic modifications on gene expression, and provides future directions in this area.

Tetracycline Analogs Inhibit Osteoclast Differentiation by Suppressing MMP-9-Mediated Histone H3 Cleavage

Osteoporosis is a common disorder of bone remodeling, caused by the imbalance between bone resorption by osteoclasts and bone formation by osteoblasts. Recently, we reported that matrix metalloproteinase-9 (MMP-9)-dependent histone H3 proteolysis is a key event for proficient osteoclast formation. Although it has been reported that several MMP-9 inhibitors, such as tetracycline and its derivatives, show an inhibitory effect on osteoclastogenesis, the molecular mechanisms for this are not fully understood. Here we show that tetracycline analogs, especially tigecycline and minocycline, inhibit osteoclast formation by blocking MMP-9-mediated histone H3 tail cleavage. Our molecular docking approach found that tigecycline and minocycline are the most potent inhibitors of MMP-9. We also observed that both inhibitors significantly inhibited H3 tail cleavage by MMP-9 in vitro. These compounds inhibited receptor activator of nuclear factor kappaB ligand (RANKL)-induced osteoclast formation by blocking the NFATc1 signaling pathway. Furthermore, MMP-9-mediated H3 tail cleavage during osteoclast differentiation was selectively blocked by these compounds. Treatment with both tigecycline and minocycline rescued the osteoporotic phenotype induced by prednisolone in a zebrafish osteoporosis model. Our findings demonstrate that the tetracycline analogs suppress osteoclastogenesis via MMP-9-mediated H3 tail cleavage, and suggest that MMP-9 inhibition could offer a new strategy for the treatment of glucocorticoid-induced osteoporosis.

β2-Adrenergic receptor (β2-AR) agonist formoterol suppresses differentiation of L6 myogenic cells by blocking PI3K-AKT pathway

β₂-Adrenergic receptor (β₂-AR) is implicated in muscle metabolic activities such as glycogen metabolism, glucose uptake, lipolysis and muscle growth. However, the functional role of β₂-AR in the differentiation of skeletal muscle is largely unknown. Here, we examined the functional role of β₂-AR in L6 myoblast differentiation using the long-term-acting β₂-AR-specific agonist formoterol. We observed that formoterol treatment strongly suppressed L6 myoblast differentiation and the expression of myosin heavy chain (MHC) in a dose- and time-dependent manner. Showing that both long-acting agonist (formoterol) and short-acting agonist (terbutaline) inhibited the induction of MHC protein, whereas β₂-AR antagonist (ICI-118,551) upregulated MHC expression, we clearly demonstrated that β₂-AR is involved in L6 myoblast differentiation. Furthermore, our pharmacological inhibition study revealed that the PI3K–AKT pathway is the main signaling pathway for myotube formation. Formoterol inhibited the activation of PI3K–AKT signaling, but not that of ERK signaling. Moreover, formoterol selectively inhibited AKT activation by IGF-I, but not by insulin. Collectively, our findings reveal a previously undocumented role of β₂-AR activation in modulating the differentiation of L6 myoblasts.

[Association between the expression of MMP1 gene and prognosis in head and neck squamous cell carcinoma]

Objective:The aim of this study is to investigate the expression of MMP1 and prognosis in patients with head and neck squamous cell carcinoma (HNSCC), and to identify the potential mechanism of MMP1 in HNSCC. Method:The RNA sequencing data and related clinical data of HNSCC were downloaded from the TCGA public database. The MMP1 gene expression data and corresponding clinical information in the samples were retrospectively analyzed; The data of gene microarray were used to verify the correlation between MMP1 gene and HNSCC. The disease free survival and overall survival of HNSCC were also analyzed; Gene set enrichment analysis was conducted to identify the potential mechanism of MMP1 in HNSCC. Result:Among the 332 HNSCC patients, the expression of MMP1 was significantly associated with lymphatic invasion and tumor grade (P<0.01). The higher the expression level of MMP1 was, the more susceptible the patient was to lymph node metastasis. The data confirmed that the expression of MMP1 in HNSCC was significantly higher than that in normal mucosa (P<0.05); HNSCC of patient in MMP1 high expression group proved to have worse disease free survival and overall survival than in MMP1 low expression group (P<0.05); Gene enrichment analysis indicates that the high expression of MMP1 gene might influence the biological process of tumor though epithelial mesenchymal transition, TGF-β signaling pathway, hypoxia, angiogenesis, Noth signaling pathway, and up-regulation of KRAS gene signaling pathway. Conclusion:The high expression of MMP1 was related with occurrence and development of HNSCC, which can be used as an independent risk factor and has a great clinical significance.

Carboxy-terminal domain of Cas differentially modulates c-Jun expression, DNA synthesis, and membrane ruffling induced by insulin, EGF, and IGF-1

p130 Crk-associated substrate (Cas) is an adaptor protein associating with many other signaling proteins and regulates a various biological processes including cell adhesion, migration, and growth factor stimulation. However, the exact functional role of Cas in growth factor signaling pathway was poorly understood. Here we investigated the role of Cas and its domains in the effects of insulin, EGF, and IGF-1 on c-Jun gene expression, DNA synthesis, cytoskeletal reorganization. We found that microinjection of anti-Cas antibody and C-terminal domain of Cas (Cas-CT) specifically inhibited EGF-induced, but not insulin- or IGF-1-induced, c-Jun expression. Cell cycle progression and cytoskeleton reorganization induced by insulin and EGF, but not by IGF-1, were inhibited by microinjected anti-Cas and Cas-CT. In contrast, microinjection of the substate domain (Cas-SD) of Cas did not have any inhibitory effects. These results revealed that the Cas-CT is differentially implicated in insulin and EGF-mediated, but not IGF-1-mediated, c-Jun expression, DNA synthesis and membrane ruffling.

Histone tail cleavage as a novel epigenetic regulatory mechanism for gene expression

Chromatin is an intelligent building block that can express either external or internal needs through structural changes. To date, three methods to change chromatin structure and regulate gene expression have been well-documented: histone modification, histone exchange, and ATP-dependent chromatin remodeling. Recently, a growing body of literature has suggested that histone tail cleavage is related to various cellular processes including stem cell differentiation, osteoclast differentiation, granulocyte differentiation, mammary gland differentiation, viral infection, aging, and yeast sporulation. Although the underlying mechanisms suggesting how histone cleavage affects gene expression in view of chromatin structure are only beginning to be understood, it is clear that this process is a novel transcriptional epigenetic mechanism involving chromatin dynamics. In this review, we describe the functional properties of the known histone tail cleavage with its proteolytic enzymes, discuss how histone cleavage impacts gene expression, and present future directions for this area of study.

[The efficacy comparation of adenoidectomy with acupuncture and tympanonstomy in children secretory otitis media]

Objective:This study aims to the comparative study of AT+A (adenoidectomy with acupuncture) and AT+T (adenoidectomy with tympanonstomy tube) to monitor and compare the therapeutic effect and prognosis of secretory otitis media in children. The study make a summary and give the clinical suggestions as well.Method:We collected and analyzed 280 outpatients of children secretory otitis media from March 2015 to March 2016.Among them,172 cases took the adenoidectomy with acupuncture and 108 cases took the adenoidectomy with tympanonstomy tube. This research used the therapeutic effect indicators,middle ear effusion time and one year follow-up to evaluate the pros and cons of two surgery methods in different areas.Result:The patients of both groups had relatively good therapeutic effect which promoted with time. There were no significant difference between AT+A and AT+T in tympanic membrane. While AT+T group acted better than AT+A group in pure tone average and tympanum figure. The middle ear effusion time of AT+T group was significantly shorter than AT+A group. In one year follow-up, there were no difference in hearing loss between two groups.But AT+T group performed better in recurrence rate, infection rate and total rate.Conclusion:Since the adenoidectomy with tympanonstomy tube method has a lot of advantages over adenoidectomy with acupuncture,it's better to use AT+T in severechildren secretory otitis media when situation is available.

Inhibition of the multidrug and toxin extrusion (MATE) transporter by pyrimethamine increases the plasma concentration of metformin but does not increase antihyperglycaemic activity in humans

We hypothesized that the pharmacodynamic (PD) characteristics of metformin would change with inhibition of the multidrug and toxin extrusion (MATE) transporter, which mediates renal elimination of metformin. Twenty healthy male subjects received two doses (750/500 mg) of metformin, with and without 50 mg of pyrimethamine (a potent MATE inhibitor), with 1 week of washout in between each dose. The PD characteristics of metformin were assessed using oral glucose tolerance tests (OGTTs) before and after the metformin dose. Metformin concentrations in plasma and urine were determined using liquid chromatography-electrospray ionization-tandem mass spectrometry. When metformin was co-administered with pyrimethamine, its area under the concentration-time curve from 0 to 12 h was 2.58-fold greater (p < 0.05), whereas the antihyperglycaemic effects of metformin were decreased. The mean differences (90% confidence interval) in mean and maximum serum glucose concentrations and in 2-h-post-OGTT serum glucose concentration were -0.6 (-1, -0.2), -0.9 (-1.6, -0.3) and -0.5 (-1.1, 0.1) mmol/l, respectively. These findings indicate that the response to metformin is not only related to the plasma exposure of metformin but is also related to other factors, such as inhibition of uptake transporters and the gastrointestinal-based pharmacology of metformin.

Epidemiological investigation of MERS-CoV spread in a single hospital in South Korea, May to June 2015

In this report, we describe 37 MERS-CoV infection cases (1 primary, 25 secondary, 11 tertiary cases) in a single hospital in South Korea. The median incubation period was six days (95% CI: 4–7 days) and the duration between suspected symptom onset and laboratory confirmation was 6.5 days (95% CI: 4–9). While incubation period was two days longer, the duration from suspected symptom onset to confirmation was shorter in tertiary compared with secondary infections.

Functional roles of BCAR3 in the signaling pathways of insulin leading to DNA synthesis, membrane ruffling and GLUT4 translocation

Breast cancer anti-estrogen resistance 3 (BCAR3) is an SH2-containing signal transducer and is implicated in tumorigenesis of breast cancer cells. In this study, we found that BCAR3 mediates the induction of ERK activation and DNA synthesis by insulin, but not by IGF-1. Specifically, the SH2 domain of BCAR3 is involved in insulin-stimulated DNA synthesis. Differential tyrosine-phosphorylated patterns of the BCAR3 immune complex were detected in insulin and IGF-1 signaling, suggesting that BCAR3 is a distinct target molecule of insulin and IGF-1 signaling. Moreover, microinjection of BCAR3 inhibitory materials inhibited membrane ruffling induced by insulin, while this did not affect insulin-mediated GLUT4 translocation. Taken together, these results demonstrated that BCAR3 plays an important role in the signaling pathways of insulin leading to cell cycle progression and cytoskeleton reorganization, but not GLUT4 translocation.

Bcr is a substrate for Transglutaminase 2 cross-linking activity

Background

Breakpoint cluster region (Bcr) is a multi-domain protein that contains a C-terminal GTPase activating protein (GAP) domain for Rac. Transglutaminase 2 (TG2) regulates Bcr by direct binding to its GAP domain. Since TG2 has transglutaminase activity that has been implicated in the response to extreme stress, we investigated if Bcr can also act as a substrate for TG2.

Results

We here report that activation of TG2 by calcium caused the formation of covalently cross-linked Bcr. Abr, a protein related to Bcr but lacking its N-terminal oligomerization domain, was not cross-linked by TG2 even though it forms a complex with it. A Bcr mutant missing the first 62 amino acid residues remained monomeric in the presence of activated TG2, showing that this specific domain is necessary for the cross-linking reaction. Calcium influx induced by a calcium ionophore in primary human endothelial cells caused cross-linking of endogenous Bcr, which was inhibited by the TG2 inhibitor cystamine. Treatment of cells with cobalt chloride, a hypoxia-mimetic that causes cellular stress, also generated high molecular weight Bcr complexes. Cross-linked Bcr protein appeared in the TritonX-100-insoluble cell fraction and further accumulated in cells treated with a proteasome inhibitor.

Conclusions

Bcr thus represents both an interacting partner under non-stressed conditions and a target of transglutaminase activity for TG2 during extreme stress.

Transglutaminase 2 regulates the GTPase-activating activity of Bcr

Transglutaminase 2 (TG2) is a multifunctional protein that has been implicated in numerous pathologies including that of neurodegeneration and celiac disease, but the molecular interactions that mediate its diverse activities are largely unknown. Bcr and the closely related Abr negatively regulate the small G-protein Rac: loss of their combined function in vivo results in increased reactivity of innate immune cells. Bcr and Abr are GTPase-activating proteins that catalyze the hydrolysis of the GTP bound to Rac. However, how the Bcr and Abr GTPase-activating activity is regulated is not precisely understood. We here report a novel mechanism of regulation through direct protein-protein interaction with TG2. TG2 bound to the Rac-binding pocket in the GTPase-activating domains of Bcr and Abr, blocked Bcr activity and, through this mechanism, increased levels of active GTP-bound Rac and EGF-stimulated membrane ruffling. TG2 exists in at least two different conformations. Interestingly, experiments using TG2 mutants showed that Bcr exhibits preferential binding to the non-compacted conformation of TG2, in which its catalytic domain is exposed, but transamidation is not needed for the interaction. Thus, TG2 regulates levels of cellular GTP-bound Rac and actin cytoskeletal reorganization through a new mechanism involving direct inhibition of Bcr GTPase-activating activity.

Bcr/Abl P190 interaction with Spa-1, a GTPase activating protein for the small GTPase Rap1

The Bcr/Abl oncogene is responsible for the development of Ph-chromosome positive acute lymphoblastic leukemia and chronic myelogenous leukemia in humans. Previous studies demonstrated that Bcr/Abl expression is associated with elevated levels of activated Rap1, a small GTPase. Levels of activated Rap1 are determined by a balance between GTPase activating and G-nucleotide exchange factor activity. We show that Bcr/Abl forms a protein-protein complex with Spa-1, a GTPase activating protein for Rap1, both in COS-1 cells as well as in primary lymphoblastic leukemia cells from a transgenic P190 BCR/ABL mouse model. The interaction between Spa-1 and P190 did not affect the tyrosine kinase activity of P190, nor did Spa-1 become phosphorylated on tyrosine as a result of the interaction. P190 and Spa-1 co-localized to peripheral actin structures in primary lymphoblasts and expression of Spa-1 in the leukemic lymphoblasts decreased the migration of these cells. The binding of Bcr/Abl to Spa-1 may cause aberrant subcellular location of Spa-1 and affect migration of these cells.

The effect of beta-cyclodextrin complexation on the bioavailability and hepatotoxicity of clotrimazole

Clotrimazole, a poorly water-soluble antimycotic agent, is a promising therapeutic agent for various diseases including cancer and sickle cell anemia. The oral bioavailability and hepatic toxicity of clotrimazole were compared with its beta-cyclodextrin inclusion form which was prepared by the spray-drying method. The inclusion complex gave significantly higher initial plasma concentrations, Cmax and AUC than did clotrimazole alone, indicating that the drug from the inclusion compound could be more easily absorbed in rats. Furthermore, mice treated with the inclusion compound showed significantly higher GOT/GPT values compared to clotrimazole alone. The inclusion compound also induced hypertrophy of hepatic cells by fat accumulation and disappearance of hepatic sinusoids, indications of pathological changes of liver, suggesting that the inclusion compound could induce more severe tissue damage in the liver than clotrimazole alone. Thus, hepatotoxicity of clotrimazole seems to be correlated with the enhanced oral bioavailability by inclusion complexation. Our results suggest that, in the development of a novel oral product, appearance or enhancement of hepatic toxicity must be considered along with oral bioavailability.

Abr and Bcr, two homologous Rac GTPase-activating proteins, control multiple cellular functions of murine macrophages

Small GTPases of the Rho family are key regulators of phagocytic leukocyte function. Abr and Bcr are homologous, multidomain proteins. Their C-terminal domain has GTPase-activating protein (GAP) activity that, in vitro, is specific for Rac and Cdc42. To address the in vivo relevance of these entire proteins, of which little is known, the current study examined the effect of the genetic ablation of Abr and Bcr in murine macrophages. The concomitant loss of Abr and Bcr induced multiple alterations of macrophage cellular behavior known to be under the control of Rac. Macrophages lacking both Abr and Bcr exhibited an atypical, elongated morphology that was reproduced by the ectopic expression of GAP domain mutant Abr and Bcr in a macrophage cell line and of constitutively active Rac in primary macrophages. A robust increase in colony-stimulating factor 1 (CSF-1)-directed motility was observed in macrophages deficient for both proteins and, in response to CSF-1 stimulation, Abr and Bcr transiently translocated to the plasma membrane. Phagocytosis of opsonized particles was also increased in macrophages lacking both proteins and correlated with sustained Rac activation. Bcr and Abr GAP mutant proteins localized around phagosomes and induced distinct phagocytic cup formation. These results identify Abr and Bcr as the only GAPs to date that specifically negatively regulate Rac function in vivo in primary macrophages.

[Ca(2+)]-dependent generation of intracellular reactive oxygen species mediates maitotoxin-induced cellular responses in human umbilical vein endothelial cells

Maitotoxin (MTX) is known as one of the most potent marine toxins involved in Ciguatera poisoning, but intracellular signaling pathways caused by MTX was not fully understood. Thus, we have investigated whether intracellular reactive oxygen species (ROS) are involved in MTX-induced cellular responses in human umbilical vein endothelial cells. MTX induced a dose-dependent increase of intracellular [Ca(2+)]. MTX stimulated the production of intracellular ROS in a dose- and time-dependent manner, which was suppressed by BAPTA-AM, an intracellular Ca(2+) che-lator. Ionomycin also elevated the ROS production in a dose-dependent manner. MTX elevated transamidation activity in a time-dependent manner and the activation was largely inhibited by transfection of tissue transglutaminase siRNA. The activation of tissue transglutaminase and ERK1/2 by MTX was sup-pressed by BAPTA-AM or ROS scavengers. In addition, MTX-induced cell death was significantly de-layed by BAPTA-AM or a ROS scavenger. These results suggest that [Ca(2+)]-dependent generation of in-tracellular ROS, at least in part, play an important role in MTX-stimulated cellular responses, such as activation of tTGase, ERK phosphorylation, and in-duction of cell death, in human umbilical vein endothelial cells.

Regulation of tissue transglutaminase by prolonged increase of intracellular Ca2+, but not by initial peak of transient Ca2+ increase

Tissue transglutaminase (tTGase) is a member of calcium-dependent transamidation enzyme family, but a detailed regulation mechanism of tTGase by intracellular Ca(2+) is not clearly understood. Arachidonic acid (AA) and maitotoxin (MTX) activated tTGase in a dose- and time-dependent manner. Transfection of tTGase siRNA largely inhibited tTGase expression and tTGase activation by MTX. AA induced an initial increase of intracellular Ca(2+) followed by a prolonged increase. Removal of extracellular Ca(2+) with EGTA blocked the prolonged Ca(2+) increase in response to AA, although the initial Ca(2+) increase remained. In contrast, EGTA completely blocked the increase of intracellular Ca(2+) by MTX. The activation of tTGase by AA or MTX was significantly inhibited by EGTA. Moreover, EGTA prevented the prolonged increase of intracellular Ca(2+) and tTGase activation by lysophosphatidic acid, but had no effect on the initial Ca(2+) increase. These results suggested that tTGase is regulated by the prolonged increase of intracellular Ca(2+) originated from Ca(2+) influx, rather than by the initial peak of transient Ca(2+) increase.

The replication of canine herpesvirus (CHV) induces apoptosis in canine kidney cell line: short communication

The alphaherpesvirus canine herpesvirus (CHV) was tested in order to determine whether or not it has apoptotic potential. We have demonstrated that lytic replication of CHV resulted in induction of apoptosis. This phenomenon was confirmed using different techniques including in situ TUNEL assay and DNA laddering. The apoptotic activity of CHV might influence the pathobiology of this virus.

Arachidonic acid activates tissue transglutaminase and stress fiber formation via intracellular reactive oxygen species

We have investigated whether arachidonic acid could regulate tissue transglutaminase (tTGase) via intracellular reactive oxygen species (ROS) in NIH3T3 cells. tTGase was identified in NIH3T3 cells by Western blot and confocal microscopy. Arachidonic acid elevated in situ tTGase activity in dose- and time-dependent manners with a maximal level at 1h, and ROS scavengers, N-(2-mercaptopropionyl)glycine and catalase, blocked the tTGase activation by arachidonic acid. The activation of tTGase by arachidonic acid was largely inhibited by transfection of tTGase siRNA. The role of intracellular ROS in the activation of in situ tTGase was supported by the activation of in situ tTGase by exogenous H(2)O(2). Arachidonic acid stimulated the formation of stress fibers in a dose- and time-dependent manner, and the ROS scavengers suppressed the arachidonic acid-induced formation of stress fibers. These results suggested that the activation of in situ tTGase and stress fiber formation by arachidonic acid was mediated by intracellular ROS in NIH3T3 cells.

Protective role of tissue transglutaminase in the cell death induced by TNF-alpha in SH-SY5Y neuroblastoma cells

Tissue transglutaminase (tTGase) regulates various biological processes, including extracellular matrix organization, cellular differentiation, and apoptosis. Here we report the protective role of tTGase in the cell death that is induced by the tumor necrosis factor alpha (TNF-alpha) and ceramide, a product of the TNF-alpha signaling pathway, in human neuroblastoma SH-SY5Y cells. Treatment with retinoic acid (RA) induced the differentiation of the neuroblastoma cells with the formation of extended neurites. Immunostaining and Western blot analysis showed the tTGase expression by RA treatment. TNF-alpha or C(2) ceramide, a cell permeable ceramide analog, induced cell death in normal cells, but cell death was largely inhibited by the RA treatment. The inhibition of tTGase by the tTGase inhibitors, monodansylcadaverine and cystamine, eliminated the protective role of RA-treatment in the cell death that is caused by TNF-alpha or C(2)-ceramide. In addition, the co-treatment of TNF-alpha and cycloheximide decreased the protein level of tTGase and cell viability in the RA-treated cells, supporting the role of tTGase in the protection of cell death. DNA fragmentation was also induced by the co-treatment of TNF-alpha and cycloheximide. These results suggest that tTGase expressed by RA treatment plays an important role in the protection of cell death caused by TNF-alpha and ceramide.

Kimchi and an Active Component, β-Sitosterol, Reduce Oncogenic H-Rasv12-Induced DNA Synthesis

The Korean fermented vegetable food, kimchi, has been demonstrated to have anticancer functional properties. This study examined the effect of kimchi samples, methanol extracts of commercially grown baechu cabbage kimchi (CK) and organically grown baechu cabbage kimchi (OK), as well as the dichloromethane fraction (DCM fr.) from CK, and the active compound (AC), which has been identified as largely beta-sitosterol, from DCM fr., on the Ras-dependent signaling pathway. CK, OK, and DCM fr. exhibited a greater inhibition against the proliferation of Rat2 fibroblasts transformed with Ras(v12) (HO6) than parental Rat2 fibroblasts. In addition, OK and DCM fr. showed a higher inhibitory effect than CK. Furthermore, we employed the single-cell microinjection technique, combined with 3-bromo-5'-deoxyuridine incorporation, to examine the effects of kimchi samples on DNA synthesis induced by microinjected oncogenic Ras(v12). When the DCM fr. and AC were used to treat Rat1 fibroblasts overexpressing human insulin receptors (HIRc-B) and microinjected with oncogenic H-Ras(v12), the DNA synthesis of injected cells was decreased, suggesting that kimchi might block the signaling pathway of oncogenic Ras(v12), thus preventing the proliferation of transformed cells. This study provides additional evidence that kimchi and its active components, including beta-sitosterol, have potential in both the prevention and treatment of cancer, and presents convincing evidence that the anticancer effects may be a result of an inhibition of Ras oncogene signaling.

Investigation of selective protein immobilization on charged protein array by wavelength interrogation-based SPR sensor

We have investigated the use of multilayer films of polyelectrolytes as selective surfaces to analyze protein interactions with a self-assembled SPR wavelength-shift sensor. Charged arrays were prepared by alternating adsorption of the charged polyelectrolytes, poly(diallyldimethylammonium chloride) (PDDA) and poly(sodium 4-styrenesulfonate) (PSS). Multilayer formation was monitored with the SPR wavelength-shift sensor and a Spreeta SPR sensor. Protein immobilization on the charged surfaces, which was also analyzed by the SPR sensors, was dependent on the pI of the proteins. Tissue transglutaminase (tTGase) and beta-galactosidase (pIs, 5.1 and 5.3, respectively) were preferentially bound to the positively charged PDDA surface, whereas lysozyme (pI, 11.0) was selectively bound to the negatively charged PSS surface. Immobilization of tTGase on the PDDA surface was also dependent on the buffer pH. The interaction of tTGase with RhoA(V14), a constitutively active form of Rho, could be detected on the charged arrays with the wavelength-shift sensor. The arrays could be reutilized at least 5 times. Thus, it is likely that charged surfaces, assembled by the layer-by-layer method using polyelectrolytes, will prove useful for preparing selective protein arrays.

Activation of in situ tissue transglutaminase by intracellular reactive oxygen species

We have investigated the novel function of intracellular reactive oxygen species (ROS) in the activation of in situ tissue transglutaminase (tTGase) by lysophosphatidic acid (LPA) and transforming growth factor-beta (TGF-beta) in Swiss 3T3 fibroblasts. LPA induced a transient increase of intracellular ROS with a maximal increase at 10 min, which was blocked by ROS scavengers, N-acetyl-L-cysteine and catalase. LPA activated tTGase with a maximal increase at 1h, which was inhibited by cystamine and ROS scavengers. Incubation with exogenous H(2)O(2) activated tTGase. TGF-beta also activated tTGase with a maximal activation at 2h and the tTGase activation was inhibited by the ROS scavengers. Scrape-loading of C3 transferase inhibited the ROS production and in situ tTGase activation by LPA and TGF-beta, and the inhibitory effect of C3 transferase was reversed by exogenous H(2)O(2). Microinjection of GTPgammaS inhibited transamidating activity of tTGase stimulated by LPA, TGF-beta, and maitotoxin. These results suggested that intracellular ROS was essential for the activation of in situ tTGase in response to LPA and TGF-beta.

Comparative anatomical study on fissura nasolacrimalis and nasomaxillaris in skull of the Korean native goat (Capra hircus)

We found specific anatomical structure on the fissura nasolacrimalis and fissura nasomaxillaris of the skull of the Korean native goat. It has quite a wide opening on each side of the os nasale and could be classified into four types according to various patterns of articulations of the neighbouring bones.

Plasmodium falciparum erythrocyte membrane protein 1 is anchored to the actin-spectrin junction and knob-associated histidine-rich protein in the erythrocyte skeleton

A distinctive pathological feature of Plasmodium falciparum malaria is the endothelial attachment of erythrocytes infected with mature asexual-stage parasites in microvessels of the major organs. Electron-dense protrusions described as knobs are displayed on the surface of parasitized erythrocytes and act as attachment points in cytoadherence. Parasite-encoded knob-associated histidine-rich protein (KAHRP) is a major component of knobs found on the cytoplasmic side of the host cell membrane. P. falciparum erythrocyte membrane protein 1 (PfEMP1) is a family of parasite-encoded cytoadherence receptors localized to knobs on the surface of parasitized erythrocytes. Despite its high antigenic diversity, PfEMP1 has a remarkably conserved cytoplasmic domain. We demonstrate in this study that the cytoplasmic domain of PfEMP1 (VAR(CD)) binds to host spectrin and actin and to full-length KAHRP in vitro. Apparent dissociation constants determined for VAR(CD)/F-actin and VAR(CD)/KAHRP interactions are 44.9+/-6.4 and 10. 7+/-2.2 nM, respectively. Further, we provide evidence that KAHRP polypeptides self-associate in solution to form structures similar to knobs and show binding of self-associated KAHRP clusters to spectrin-actin-protein 4.1 complexes. Findings in this study suggest that PfEMP1 is localized to the knob in P. falciparum-infected erythrocytes by binding to the host spectrin-actin junction and to self-associated KAHRP through its conserved cytoplasmic domain.

The coexistence of calcitonin gene-related peptide and substance P in pericellular arborization and satellite cell of goat trigeminal and nodose ganglia

Pericellular arborization is reported to be the self-regulating structure in sensory ganglia. Although the calcitonin gene-related peptide (CGRP) or substance P (SP) immunoreactive pericellular arborization appeared in the sensory ganglia, there was no available information that CGRP and SP colocalize in this structure. As the attempts to resolve the question described above, the present study was undertaken to identify the coexistence of CGRP and SP in pericellular arborizations of the goat nodose and trigeminal ganglia by double immunohistochemistry. As the results show, CGRP immunoreactivity was present in every pericellular arborization containing SP immunoreactivity in trigeminal ganglia, however, pericellular network containing CGRP or SP immunoreactivity was not present in nodose ganglia. Unexpectedly, a few small satellite elements were observed to contain intense CGRP and SP immunoreactivity at the periphery of CGRP and SP immunoreactive neurones in nodose ganglia. Therefore, these results suggest that CGRP and SP coexist in pericellular arborizations, and that satellite cell as well as pericellular arborization may be involved in intraganglionic regulation of goat sensory ganglia.

The comparative anatomical study of the parietal region of the skull of the Korean native goat (Capra hircus)

In the skull of the Korean native goat, the parietal region was classified into four types by the degree of the fusion of the bones, the os interparietale, the os parietale and the squama occipitalis of the os occipitale, and the structural variations of these fusions. The fusion appeared first in the sutura interparietoparietalis and that of the sutura sagittalis of both ossa parietalia was followed. There was no fusion between the os parietale and the squama occipitalis of the os occipitale. These results suggest that the os interparietale developed independently but fused to the os parietale after birth, and the os parietale were developed as paired bones in prenatal life and then fused together according to age.

Temporal synthesis of band 3 oligomers during terminal maturation of mouse erythroblasts. Dimers and tetramers exist in the membrane as preformed stable species

Band 3, the anion transport protein of the erythrocyte membrane, exists in the membrane as a mixture of dimers (B3D) and tetramers (B3T). The dimers are not linked to the skeleton and constitute the free mobile band 3 fraction. The tetramers are linked to the skeleton by their interaction with ankyrin. In this report we have examined the temporal synthesis and assembly of band 3 oligomers into the plasma membrane during red cell maturation. The oligomeric state of newly synthesized band 3 in early and late erythroblasts was analyzed by size-exclusion high-pressure liquid chromatography of band 3 extracts derived by mild extraction of plasma membranes with the nonionic detergent C12E8 (octaethylene glycol n-dodecyl monoether). This analysis revealed that at the early erythroblast stage, the newly synthesized band 3 is present predominantly as tetramers, whereas at the late stages of erythroid maturation, it is present exclusively as dimers. To examine whether the dimers and tetramers exist in the membrane as preformed stable species or whether they are interconvertible, the fate of band 3 species synthesized during erythroblast maturation was examined by pulse-chase analysis. We showed that the newly synthesized band 3 dimers and tetramers are stable and that there is no interconversion between these species in erythroblast membranes. Pulse-chase analysis followed by cellular fractionation showed that, in early erythroblasts, the newly synthesized band 3 tetramers are initially present in the microsomal fraction and later incorporated stably into the plasma membrane fraction. In contrast, in late erythroblasts the newly synthesized band 3 dimers move rapidly to the plasma membrane fraction but then recycle between the plasma membrane and microsomal fractions. Fluorescence photobleaching recovery studies showed that significant fractions of B3T and B3D are laterally mobile in early and late erythroblast plasma membranes, respectively, suggesting that many B3T-ankyrin complexes are unattached to the membrane skeleton in early erythroblasts and that the membrane skeleton has yet to become tightly organized in late erythroblasts. We postulate that in early erythroblasts, band 3 tetramers are transported through microsomes and stably incorporated into the plasma membrane. However, when ankyrin synthesis is downregulated in late erythroblasts, it appears that B3D are rapidly transported to the plasma membrane but then recycled between the plasma membrane and microsomal compartments. These observations may suggest novel roles for membrane skeletal proteins in stabilizing integral membrane protein oligomers at the plasma membrane and in regulating the endocytosis of such proteins.

Rac GTPase activity is essential for EGF-induced mitogenesis

Rac, a member of the Rho family GTPases, has been implicated in the regulation of a wide range of biological processes including actin remodeling, cell transformation, G1 cell cycle progression, and gene expression. To determine whether Rac GTPase activity is required for epidermal growth factor-induced mitogenesis, Rat-2 stable cells expressing a dominant-negative Rac1 mutant, RacN17, were prepared. Exposure to EGF exhibited a significantly restricted growth response in Rat-2-RacN17 cells compared to Rat-2 parental cells, suggesting an essential role of Rac in EGF-induced mitogenesis. In contrast, addition of lysophosphatidic acid exerted the same level of growth in Rat-2 and Rat-2-RacN17 cells. To gain further evidence for the essential role of Rac in EGF-induced mitogenesis, we performed the microinjection experiment. EGF-induced DNA synthesis was significantly blocked by microinjection of recombinant RacN17 protein, and not control IgG. Our further study to analyze the downstream mediator of Rac in EGF-signaling to mitogenesis demonstrated that Rac-activated phospholipase A2 plays a critical role. Taken together, our results suggest that the "Rac and Rac-activated PLA2" cascade is one of the major mitogenic pathways induced by EGF.

Red cell membranes of ankyrin-deficient nb/nb mice lack band 3 tetramers but contain normal membrane skeletons

The role of ankyrin in the formation and stabilization of the spectrin-based skeletal meshwork and of band 3 oligomers was studied by characterizing, in nb/nb mouse red cells, the effect of ankyrin deficiency on skeletal ultrastructure, band 3-skeleton associations, and band 3 oligomeric states. Despite severe ankyrin deficiency, nb/nb mouse red cell skeletal components formed a relatively uniform two-dimensional hexagonal array of junctional complexes cross-linked by spectrin tetramers. Treatment of nb/nb ghosts with the nonionic detergent C12E8 (octaethylene glycol n-dodecyl monoether) resulted in nearly complete extraction of band 3. The extracted band 3 was present exclusively as band 3 dimers. Fluorescence photobleaching recovery and polarized fluorescence depletion measurements showed increases in the laterally (33% vs 10%) and rotationally (90% vs 76%) mobile fractions of band 3 in intact nb/nb compared to control red cells. The rotational correlation time of the major fraction of band 3 molecules was 10-fold shorter in nb/nb compared to control red cells, indicating a significant relaxation of rotational constraints in nb/nb cells. These data suggest that, although ankyrin plays a major role in strengthening the attachment of the skeleton to the membrane bilayer, ankyrin is not required for the formation of a stable two-dimensional spectrin-based skeleton. The absence of band 3 tetramers in the membrane of ankyrin-deficient red cells suggests that ankyrin is required for the formation of stable band 3 tetramers.

Targeted disruption of the murine erythroid band 3 gene results in spherocytosis and severe haemolytic anaemia despite a normal membrane skeleton

Band 3 is the most abundant integral protein of the red blood cell membrane. It performs two critical biological functions: maintaining ionic homeostasis, by transporting Cl- and HCO3-ions, and providing mechanical stability to the erythroid membrane. Erythroid band 3 (AE1) is one of three anion exchangers that are encoded by separate genes. The AE1 gene is transcribed by two promoters: the upstream promoter produces erythroid band 3, whereas the downstream promoter initiates transcription of the band 3 isoform in kidney. To assess the biological consequences of band 3 deficiency, we have selectively inactivated erythroid but not kidney band 3 by gene targeting in mice. Although no death in utero occurred, the majority of homozygous mice die within two weeks after birth. The erythroid band 3 null mice show retarded growth, spherocytic red blood cell morphology and severe haemolytic anaemia. Remarkably, the band 3-/- red blood cells assembled normal membrane skeleton thus challenging the notion that the presence of band 3 is required for the stable biogenesis of membrane skeleton. The availability of band 3-/- mice offers a unique opportunity to investigate the role of erythroid band 3 in the regulation of membrane-skeletal interactions, anion transport and the invasion and growth of malaria parasite into red blood cells.

Hereditary spherocytosis with spectrin deficiency due to an unstable truncated beta spectrin

Red cell membrane protein analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and direct quantitation by radioimmunoassay or cytofluorometry defines four distinct subsets of patients with hereditary spherocytosis: Patients with isolated spectrin deficiency, combined spectrin and ankyrin deficiency, band 3 deficiency, and protein 4.2 deficiency. In regard to the first group, only one mutation of beta spectrin has been reported in the literature. We describe a spectrin variant characterized by a truncated beta chain, and associated with hereditary spherocytosis and isolated spectrin deficiency. The clinical phenotype consists of a moderate hemolytic anemia with spherocytosis and frequent spiculation of the red cells. We present the biochemical characteristics of this mutant protein and show that it constitutes only 12% of the total spectrin on the membrane. We show that the truncation of the protein is the result of a single point mutation at position +1 (G-->A) of the donor consensus splice site of intron 17 leading to an aberrant beta spectrin transcriptional message lacking exons 16 and 17. To elucidate the basis for the decreased amount of the truncated protein on the membrane and the overall spectrin deficiency, we provide evidence that the mutated gene is transcribed but its mRNA is less abundant than its normal counterpart in reticulocytes; we also show that the mutant protein is synthesized in decreased amounts in the cytoplasm of erythroid progenitor cells, and appears to be susceptible to proteolytic degradation. This mutant spectrin underscores the importance of the regulatory role played by the beta spectrin molecule in the assembly of alphabeta spectrin heterodimers on the membrane.

Developmental profile of messenger RNA for the corticotropin-releasing hormone receptor in the rat limbic system

The ontogeny of corticotropin-releasing hormone (CRH) receptor messenger ribonucleic acid (mRNA) in rat brain, using in situ hybridization, is the focus of this study. The developmental profile of CRH receptor using binding assays and receptor autoradiography has been reported, but may be confounded by the presence of a binding protein. The recent cloning of the rat CRH receptor gene has permitted the use of in situ hybridization histochemistry to map the distribution of cells expressing CRH receptor mRNA in the developing brain. We used antisense 35S-labeled oligodeoxynucleotide probes for the two reported splice-variants of the CRH receptor mRNA, which yielded essentially identical localization patterns. CRH receptor mRNA was clearly detectable in infant brain starting on the second postnatal day. Signal in hippocampal CA1, CA2 and CA3a increased to 300-600% of adult levels by postnatal day 6 with a subsequent gradual decline. In the amygdala, in contrast, CRH receptor mRNA abundance increased steadily between the second and the ninth postnatal days, to levels twice higher than those in the adult. In the cortex, CRH receptor mRNA levels were high on postnatal day 2 and decreased to adult levels by day 12. Transient signal over the hypothalamic paraventricular nucleus, observed on the second postnatal day, was not evident at older ages. These results demonstrate robust synthesis of CRH receptor as early as on the second postnatal day and unique region-specific developmental profiles for CRH receptor gene expression.

Developmental profile of corticotropin releasing hormone messenger RNA in the rat inferior olive

Corticotropin releasing hormone is a neurotransmitter in the inferior olive complex of marsupials and mammals. The ontogeny of corticotropin releasing hormone gene expression in the rat inferior olive has not been described. Using in-situ hybridization histochemistry in 25 animals, we established the developmental profile of the peptide's messenger ribonucleic acid in the postnatal rat. CRH-messenger RNA was first detectable in two of four animals on the fifth postnatal day. Subsequently, gene expression increased linearly with age: by day 14, CRH was expressed in all olivary complex nuclei, and the distribution and relative abundance on day 18 were comparable to those in the adult. The developmental profile of CRH-mRNA in the rat inferior olive differs from those in the mouse and opossum, and from the pattern in the rat hypothalamus, suggesting species- and site-specificity of the peptide's function.

Red cell membrane remodeling in sickle cell anemia. Sequestration of membrane lipids and proteins in Heinz bodies

In red cells from patients with sickle cell anemia, hemoglobin S denatures and forms Heinz bodies. Binding of Heinz bodies to the inner surface of the sickle cell membrane promotes clustering and colocalization of the membrane protein band 3, outer surface-bound autologous IgG and, to some extent, the membrane proteins glycophorin and ankyrin. Loss of transbilayer lipid asymmetry is also found in certain populations of sickle red cells. The lateral distribution of sickle cell membrane lipids has not been examined, however. In this report, we examine by fluorescence microscopy the incorporation and distribution of the fluorescent phospholipid analogues 7-nitro-2,1,3-benzoxadiazol-4-yl (NBD)-phosphatidylserine and NBD-phosphatidylcholine in sickle red cells. Both phospholipid analogues are observed to accumulate prominently at sites of Heinz bodies. Accumulation at sites of Heinz bodies is also shown by 1,'1-dihexadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate, a fluorescent lipid analogue that readily crosses membranes, but not by fluorescein-phosphatidylethanolamine, an analogue that is localized to the outer leaflet of the membrane. Double labeling and confocal microscopy techniques show that NBD-lipids, band 3 protein, protein 4.1, ankyrin, and spectrin are all sequestered within sickle red cells and colocalized at sites of Heinz bodies. We propose that Heinz bodies provide a hydrophobic surface on which sickle red cell membrane lipids and proteins are sequestered.

Molecular basis of spectrin deficiency in beta spectrin Durham. A deletion within beta spectrin adjacent to the ankyrin-binding site precludes spectrin attachment to the membrane in hereditary spherocytosis

We describe a spectrin variant characterized by a truncated beta chain and associated with hereditary spherocytosis. The clinical phenotype consists of a moderate hemolytic anemia with striking spherocytosis and mild spiculation of the red cells. We describe the biochemical characteristics of this truncated protein which constitutes only 10% of the total beta spectrin present on the membrane, resulting in spectrin deficiency. Analysis of reticulocyte cDNA revealed the deletion of exons 22 and 23. We show, using Southern blot analysis, that this truncation results from a 4.6-kb genomic deletion. To elucidate the basis for the decreased amount of the truncated protein on the membrane and the overall spectrin deficiency, we show that (a) the mutated gene is efficiently transcribed and its mRNA abundant in reticulocytes, (b) the mutant protein is normally synthesized in erythroid progenitor cells, (c) the stability of the mutant protein in the cytoplasm of erythroblasts parallels that of the normal beta spectrin, and (d) the abnormal protein is inefficiently incorporated into the membrane of erythroblasts. We conclude that the truncation within the beta spectrin leads to inefficient incorporation of the mutant protein into the skeleton despite its normal synthesis and stability. We postulate that this misincorporation results from conformational changes of the beta spectrin subunit affecting the binding of the abnormal heterodimer to ankyrin, and we provide evidence based on binding assays of recombinant synthetic peptides to inside-out-vesicles to support this model.

Molecular basis of altered red blood cell membrane properties in Southeast Asian ovalocytosis: role of the mutant band 3 protein in band 3 oligomerization and retention by the membrane skeleton

Southeast Asian ovalocytosis (SAO) is an asymptomatic trait characterized by rigid, poorly deformable red cells that resist invasion by several strains of malaria parasites. The underlying molecular genetic defect involves simple heterozygous state for a mutant band 3 protein, which contains a deletion of amino acids 400 through 408, linked with a Lys 56-to-Glu substitution (band 3-Memphis polymorphism). To elucidate the contribution of the mutant SAO band 3 protein to increased SAO red blood cell (RBC) rigidity, we examined the participation of the mutant SAO band 3 protein in increased band 3 attachment to the skeleton and band 3 oligomerization. We found first that SAO RBC skeletons retained more band 3 than normal cells and that this increased retention preferentially involved the mutant SAO band 3 protein. Second, SAO RBCs contained a higher percentage of band 3 oligomer-ankyrin complexes than normal cells, and these oligomers were preferentially enriched by the mutant SAO protein. At the ultrastructural level, the increased oligomer formation of SAO RBCs was reflected by stacking of band 3-containing intramembrane particles (IMP) into longitudinal strands. The IMP stacking was not reversed by treating SAO RBCs in alkaline pH (pH 11), which is known to weaken ankyrin-band 3 interactions, or by removing the cytoplasmic domain of band 3 from SAO membranes with trypsin. Finally, we found that band 3 protein in intact SAO RBCs exhibited a markedly decreased rotational mobility, presumably reflecting the increased oligomerization and the membrane skeletal association of the SAO band 3 protein. We propose that the mutant SAO band 3 has an increased propensity to form oligomers, which appear as longitudinal strands of IMP and exhibit increased association with membrane skeleton. This band 3 oligomerization underlies the increase in membrane rigidity by precluding membrane skeletal extension, which is necessary for membrane deformation.

Effects of maternal and sibling deprivation on basal and stress induced hypothalamic-pituitary-adrenal components in the infant rat

Prolonged maternal deprivation during early infancy increases basal- and stress-induced corticosterone (CORT) levels, but the underlying mechanism is not clear. In general, stressors activate the hypothalamic-pituitary-adrenal (HPA) axis, with secretion and compensatory synthesis of hypothalamic cortcotropin-releasing hormone (CRH). In the infant rat, we have demonstrated that maximally tolerated acute cold stress induced a robust elevation of plasma CORT throughout the first 2 postnatal weeks. However CRH messenger RNA (CRH-mRNA) abundance 4 h subsequent to cold stress was enhanced only in rats aged 9 days or older. This suggests a developmental regulation of the CRH component of the HPA-response to this stressor. The present study examined whether increased basal and cold stress-induced CORT levels after 24 h of maternal deprivation were due to enhanced CRH-mRNA abundance in the hypothalamic paraventricular nucleus (PVN). CRH-mRNA abundance, and basal- and cold-induced plasma CORT levels were measured in maternally deprived 6 and 9-day-old pups compared to non-deprived controls. Maternal deprivation increased basal and cold-induced CORT levels on both 6 and 9-day-old rats. CRH-mRNA abundance in the PVN of deprived rats did not differ from that in non-deprived rats. Our results indicate that the enhanced basal and stress-induced plasma CORT observed after 24 h maternal deprivation is not due to increased CRH-mRNA abundance in the PVN.