Browsing by Subject "regulation"
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Item Akt Isoforms: A Family Affair in Breast Cancer(MDPI, 2021-07-09) Basu, Alakananda; Lambring, Christoffer B.Akt, also known as protein kinase B (PKB), belongs to the AGC family of protein kinases. It acts downstream of the phosphatidylinositol 3-kinase (PI3K) and regulates diverse cellular processes, including cell proliferation, cell survival, metabolism, tumor growth and metastasis. The PI3K/Akt signaling pathway is frequently deregulated in breast cancer and plays an important role in the development and progression of breast cancer. There are three closely related members in the Akt family, namely Akt1(PKBalpha), Akt2(PKBbeta) and Akt3(PKBgamma). Although Akt isoforms share similar structures, they exhibit redundant, distinct as well as opposite functions. While the Akt signaling pathway is an important target for cancer therapy, an understanding of the isoform-specific function of Akt is critical to effectively target this pathway. However, our perception regarding how Akt isoforms contribute to the genesis and progression of breast cancer changes as we gain new knowledge. The purpose of this review article is to analyze current literatures on distinct functions of Akt isoforms in breast cancer.Item Combining Injectable Plasma Scaffold with Mesenchymal Stem/Stromal Cells for Repairing Infarct Cavity after Ischemic Stroke(JKL International, 2017-04-01) Zhang, Hongxia; Sun, Fen; Wang, Jixian; Xie, Luokun; Yang, Chenqi; Pan, Mengxiong; Shao, Bei; Yang, Guo-Yuan; Yang, Shaohua; Zhuge, Qichuan; Jin, KunlinStroke survivors are typically left with structural brain damage and associated functional impairment in the chronic phase of injury, for which few therapeutic options exist. We reported previously that transplantation of human embryonic stem cell (hESC)-derived neural stem cells together with Matrigel scaffolding into the brains of rats after focal ischemia reduced infarct volume and improved neurobehavioral performance. Matrigel is a gelatinous protein mixture extracted from mouse sarcoma cells, thus would not be approved for use as a scaffold clinically. In this study, we generated a gel-like scaffold from plasma that was controlled by changing the concentration of CaCl2. In vitro study confirmed that 10-20 mM CaCl2 and 10-40% plasma did not affect the viability and proliferation of human and rat bone marrow mesenchymal stem/stromal cells (BMSCs) and neural stem cells (NSCs). We transplanted plasma scaffold in combination of BMSCs into the cystic cavity after focal cerebral ischemia, and found that the atrophy volume was dramatically reduced and motor function was significantly improved in the group transplanted with scaffold/BMSCs compared with the groups treated with vehicle, scaffold or BMSCs only. Our data suggest that plasma-derived scaffold in combination of BMSCs is feasible for tissue engineering approach for the stroke treatment.Item Differential Gene Expression Profiling in a Small Animal Model of Progressively Pacing-Induced Heart Failure(2006-06-01) Selby, Donald Evan; Stephen R. Grant; Patricia A. Gwirtz; Dan DimitrijevichDonald Evan Selby, Differential Gene Expression Profiling in a Small Animal Model of Progressively Pacing-Induced Heart Failure. Doctor of Philosophy (Biomedical Sciences), July 2006, 235 pp, 4 tables, 35 illustrations, references, 328 titles. Pacing induced tachycardia (PIT), in mammals, is known to cause a change from normal heart function to early left ventricular dysfunction. Progression to heart failure in experimental animals, such as dogs, pigs, and sheep, takes place in a relatively short period of time compared to the disease development observed in humans. Due to the cost and nature of using such animals, there is a need for a small animal model of PIT, which would delineate the etiology of the disease state by impairing the systolic function. The mode of action of overpacing inducement of cardiomyopathy, as the data suggests, may be through a sarcomere stretch sensor and its length-dependent signaling mechanism. In this study, an internal electrical-overpacing of an isogenic rabbit strain over a 52-day period was used to initiate a pathology consistent with human CHF. The data presented demonstrated that PIT causes alterations in the systolic ability of the heart, observed as reduced fractional shortening of the heart. This is seen in changes of the message pool population for proteins of the contractile architecture. Initially the heart is being paced rapidly and therefore there is insufficient time to get blood into the chamber. Thus, the data suggests that a mechanical stretch sensor is the process by which overpacing the heart leads to changes in gene expression which ultimately cause a compounding cellular condition which exists during heart failure. The data shows that there are gene isoform ratio changes that occur as the disease develops these include changes in differential expression of cardiac titin alternative splicing isoforms. The data suggests that there is also isoform switching occurring with alternative splicing of the gene encoding for SERCA2a, the probe 1587641_at shows a moderate decrease in expression and using BLAST for this probe this sequence is homologous to an alternative splicing variant of SERCA2a of the rabbit accession number J04703. The data shows that ferritin heavy chain also has an alternative splicing variant that are differentially regulated, this dysregulation of the isoform ratio may be linked to ADAMSTS1, a disintegrin and metalloproteinase isoform 1, which is seen to be downregulated in the data, these play a role in negative regulation of cellular proliferation. In addition to these detected isoform changes in the ratios of alternative splice variants changes are seen in genes linked to sarcomere integrity such as dystrophin probe 1582958_at is significantly increased in its expression, also integrin beta-1 probe 1584175)at shows a marginal increase in expression. The protease calpain probe 1604384)at, which uses a substrate the aforementioned integrin, dystrophin, and titin is also significantly upregulated in the data. Interestingly calpastatin, probe 1591603_at the inhibitor of calpain is marginally increased in its expression. Only recently has titin become to be appreciated as the protein that is responsible for the Frank Starling law as it undergoes an isoform ratio change as heart failure develops. These changes are initially caused by changes in ion concentration and stress upon the contractile proteins but as seen in the study, leads to altered gene expression. In this model, these gene alterations lead to diastolic dysfunction and the compounded problems constitute heart failure. This work shows that heart failure induced by over-pacing creates physical demands upon the framework of the heart and these physical stresses are transmitted through mechanical sensors leading to differential expression of the message pools for proteins involved in the way the heart contracts, and fills upon relaxation which ultimately ends in a heart that can do neither, thus leading to death.Item Identifying and Overcoming Barriers in Clinical Research Management: A Review of Clinical Trials within an Academic Medical Center(2008-12-01) Hatfield, ElishaOver the decades, clinical research has grown and evolved into what one would consider now as the cornerstone of medical advancement. Through the use of clinical trials, new and improved prevention and treatments continue to be discovered. These trials are not only an essential part of the process of drug discovery and development, but are required for drug approval. Conducting these clinical trials takes diligent cooperation between the pharmaceutical industry, government agencies, investigators, and academic medical centers (AMC’s). With the implementation of new regulations as well as continual changes to policies and procedures overseeing clinical research, management of such trials has become a very meticulous and a lengthy process. Additionally, escalating costs of drug development and an increased need for new treatments in the market at faster rates have made the need for more effective and productive means of conducting clinical trials a priority for competitive research sites. With the landscape of clinical research constantly evolving, adaptation of study management and procedures is a continuous hurdle that clinical research sites must overcome. Changes in regulations, limitations of funds and the need for more effective subject recruitment methods are all barriers that most AMC’s are facing today. Finding ways to overcome these obstacles is an essential part of conducting effective and productive clinical trials. In order to keep up with this change and maintain a high quality of research, continual review and audit of current research standards and procedures has become a necessity. Review of standard operating procedures and study documentation can help identify barriers which inhibit the process and initiate appropriate modifications in order to maintain efficient and effective study trials. As such, for this Internship Practicum Project, the intern reviewed the standard procedures and monitored clinical studies with the Gastrointestinal Disease Oriented Team (GI DOT) in an attempt to identify barriers affecting the overall productivity and efficiency of the team. Once these barriers had been outlined, recommendations for changes in standard procedures were made in order to help improve the functionality of the GI DOT and, subsequently, enhance the success of GI protocols within the Simmons Cancer Center Clinical Research Office.Item Post-transcriptional and Epigenetic Regulation of MIEN1 in Prostate Cancer(2014-08-01) Rajendiran, Smrithi; Vishwanatha, Jamboor K.; Basu, Alakananda; Berg, Rance E.Migration and invasion enhancer 1 (MIEN1), a gene located in the 17q12 region of the human chromosome, enhances migratory and invasive potential of cancer cells via two mechanisms; activating the Akt dependent NF-κB downstream signaling and facilitating filopodia formation; thereby playing an important role in cancer progression. MIEN1 is highly expressed in many cancers including prostate and breast, but its expression is very basal to null in a variety of normal tissues making it a plausible target for cancer therapy. Though the functions of MIEN1 are known, the reasons for its increased expression in cancer is unknown. Determining the molecular gene regulatory mechanisms by which expression of MIEN1 is curtailed in normal cells will help in developing better targeting strategies. Among the different gene regulatory mechanisms including transcriptional regulation, post-transcriptional modifications and histone and DNA alterations, here we focus on post transcriptional and DNA methylation based regulation of MIEN1. We show that MIEN1 is downregulated post-transcriptionally by miRNA-940 which itself is present in low amounts in cancer cells and tissues compared to the normal counterparts. The miR-940 also contributes to inhibition of cancer progression by attenuating the migration, invasion, anchorage-independent growth and epithelial-to-mesenchymal transition, when ectopically re-introduced into cancer cells. The miR-940 can be detected in circulation and its elevated levels in serum from cancer patients than normal subjects, suggest its potential as a biomarker for prostate cancer diagnosis. MIEN1, like urokinase plasminogen activator, is also suppressed by DNA methylation in normal cells. On the contrary, hypomethylation in cancer, results in its overexpression. The current approach of using global demethylating agents to activate the expression of hypermethylated tumor suppressor genes may in the long run activate tumor promoting genes like MIEN1. Thus, our study supports the notion that gene-centric hypomethylating agents may be a better epigenetic targeting approach to treat cancer. In conclusion, our data confirm the role of post-transcriptional and DNA methylation mediated mechanisms in the regulation of MIEN1.Item Protein Phosphate in the Regulation of Protein Phosphorylation and Insulin Secretion(2003-05-01) Parameswara, Vinay K.; Robert Easom; Porunelloor Mathew; Ming-Chi WuParameswara, Vinay K., Protein Phosphatase 2A in the Regulation of Ca2+- Sensitive Protein Phosphorylation and Insulin Secretion. Doctor of Philosophy (Biomedical Sciences), May 2003; 191 pp., 28 illustrations; 5 tables; 250 references. Type 2 diabetes is characterized by insufficient insulin secretion in the midst of increased demand from concomitant insulin resistance of peripheral tissues. More specifically, the diabetic β-cell is characterized by impaired responsiveness to D-glucose, the primary physiological regulator of insulin secretion, necessitating that the mechanism of glucose-induced insulin secretion from the β-cell of the pancreas is critically dependent on an elevation of cytosolic calcium as a trigger signal but is also dependent on reversible protein phosphorylation. Accordingly, a number of protein kinases are activated by glucose, or by incretin hormones that enhance glucose-induced insulin secretion. This dissertation however stems from a general hypothesis that protein phosphorylation and insulin secretion may also be controlled via the regulation of protein phosphatases (PP). Initially, a panel of specific antibodies was used to profile the expression of known PP species in the β-cell. By immunoblotting cultured clonal β-cells, INS-1, were shown to express various protein phosphatases namely PP 1, 2A, 2B, 2C, 4 and 6, but with distinct subcellular localization suggesting that these phosphatases regulated distinct functions within the β-cells. Of particular interest, PP-2A holoenzyme was localized to purified fractions of insulin secretory granules suggesting an involvement in insulin regulation. Selective inhibition of PP-2A in the presence of endothall or low concentrations of okadaic acid, increased insulin secretion in the presence of glucose in INS-1 cells. In order to discern potential substrates of PP-2A and thus-mechanisms of action, microcystin immobilized to sepharose was employed to affinity purify phosphatase species from β-cell lysates and proteins complexed with them. Fractions containing PP-2A also contained synapsin I and a specific interaction of these proteins was confirmed by co-immunoprecipitation from INS-1 cell lysates. In contrast, PP-1 was not associated with synapsin I. That synapsin I is indeed a substrate for PP-2A in INS-1 cells was confirmed via the demonstration that synapsin I phosphorylation was increased by okadaic acid under conditions that increased insulin release. Okadaic acid also induced the autophosphrylation and activation of CaMKII, a Ca2+-dependent kinase that phosphorylates synapsin I; suggesting CaMKII may mediate PP-2A effects on insulin secretion. The elimination of syanpsin I, markedly modulates glucose homeostasis of mice and subtly modulates insulin release. In summary these studies document that the modulation of PP-2A in β-cells dramatically influences insulin secretion reinforcing a concept that the control of protein phosphatase may have a critical role in the regulation of insulin secretion. These data suggest that a role of PP-2A on insulin secretion is mediated in part through the regulation of CaMKII activity and synapsin I-phosphorylation.Item Regulation of Myocardial Blood Flow and Function During Exercise in Dogs(1995-06-01) Kim, Song-Jung; Patricia A. Gwirtz; Peter B. Raven; James L. CaffreyIntroduction. Background. Coronary circulation during exercise. Coronary blood flow is regulated primarily by local metabolic mechanisms according to the oxygen and nutrient needs of the heart (2, 4, 19). The local “metabolic signal” involves vasoactive metabolites, such as adenosine, released from myocytes in direct proportion to myocardial work (Figure 1). However, other external factors are superimposed on local regulatory mechanisms and can substantially modulate coronary blood flow. One of these modulatory factors is the sympathetic nervous system. Sympathetic vasoconstriction mediated by α-adrenergic receptors in the coronary circulation has been shown to oppose metabolic vasodilation and limit oxygen supply to the myocardium during physiologic and pathophysiological cardiac stresses, such as exercise and myocardial hypoperfusion (1, 6, 7, 8, 10-14, 17, 18, 21). This limitation on myocardial oxygenation appears to impose a restriction on the increase in regional left ventricular subendocardial contractile function during submaximal exercise (7). In this regard, studies have shown that removing this α1-constrictor tone leads to an increase in coronary blood flow and, as a result, regional contractile function (8). This adrenergic coronary constriction during exercise is mediated by neutrally released norepinephrine, not by circulating catecholamines (8). Endothelial-mediated control of coronary vascular tone. Recent investigations indicate that another factor involved in modulating coronary blood flow is the vascular endothelium. The endothelium exerts an influence on vascular smooth muscle vasomotor tone by releasing an endothelium-derived relaxing factor (EDRF) or nitric oxide (NO), which is derived from the amino acid L-arginine by nitric oxide synthase (5, 22). Synthesized NO diffuses into the underlying vascular smooth muscle to activate cytosolic guanylate cyclase (GC), thereby stimulating the intracellular accumulation of cyclic GMP (cGMP). This is illustrated in Figure 2. NO is released by the stimulation of muscarinic receptors on endothelial cells by acetylcholine, as well as by other agonists or physical stimuli (e.g., shear stress) at the interface between blood and endothelial cell surface (15). During exercise, for example, the work output of the normal heart may increase several-fold by the stimulation of sympathetic nerves to heart. The increased work output of the heart increases myocardial oxygen demand. Consequently, the coronary circulation undergoes vasodilation due to local metabolic mechanisms. The elevation in shear stress caused by increases in coronary blood flow triggers release of NO from the endothelium because of the extremely pulsatile nature of the flow. Therefore, it is likely that during exercise, release of NO by shear stress and by neurohormonal stimuli, concomitant with local release of metabolites, contributes to coronary dilation. These vasodilatory influences counteract a sympathetic α-adrenergic coronary constriction, which limits the increase in coronary blood flow and cardiac performance. Accordingly, coronary vascular smooth muscle tone during exercise is modulated by the endothelium, which responds to the increased shear stress and adrenergic stimulation, which provides the major extrinsic input.Item REGULATION OF PROTEIN KINASE C-ETA IN BREAST CANCER(2013-04-12) Pal, DeepanwitaPurpose: The protein kinase C (PKC) and phosphotidylinositide-3 kinase (PI3K) signaling pathways play critical roles in the development of breast cancer and regulate cell proliferation, differentiation, cell death and tumor promotion. PKCs serve as receptors for tumor-promoting phorbol esters, which are potent activators of conventional and novel members of the PKC family, and can substitute for the physiologic activator diacylglycerol. Prolonged treatment with phorbol esters, however, induces downregulation of these PKCs. Protein kinase C-eta is a novel member of the PKC family but resists downregulation by phorbol esters. This unique regulation of PKC-eta may have implications in tumor promotion. PKCs are regulated not only by cofactors but also by phosphorylation. Phosphorylation and dephosphorylation of PKCs can regulate their activity, stability and function. The objective of this study is to understand the regulation and contribution of PKC-eta in breast cancer. Methods: Established breast cancer cell lines were used in our study. The effect of distinct kinase inhibitors on PKCη protein levels was determined by Western blot analysis. The effect of proteasome and protease inhibitors on PKC-eta levels was also assessed by Western blotting. RNAi technique was utilized to knockdown members of the PKC and PI3K pathways. MTT assay was performed to determine the effect of PKC-eta on cell growth while cell proliferation upon PKC-eta knockdown was monitored by clonogenic assay. Results: Inhibition of PKC and PI3K pathways induced downregulation of PKC-eta via two distinct mechanisms. PKC-eta depletion inhibited the growth and proliferation of breast cancer cells. Conclusions: Our results demonstrate that the distinct regulation of PKC-eta by members of the PKC and PI3K family contributes to breast cancer cell growth.Item Sigma-1 Receptor Signaling in the Eye(2008-03-12) Tchedre, Kissaou T.; Yorio, Thomas; Singh, Meharvan; Machu, TinaSIGMA-1 Receptor Signaling in the Eye Kissaou T. Tchedre, Department of Biomedical Sciences, University of North Texas Health Science Center Fort Worth, TX 76107. SUMMARY The sigma-1 receptor is a discovered transmembrane protein that mediates the regulation of ion channels. Sigma-1 receptor ligands have exhibited a wide variety of actions in the central nervous system including attenuation of the neuronal death associated with glutamate excitotoxicity both in vitro and in vivo. Although the sigma-1 receptor was cloned almost a decade ago, the molecular mechanism of the neuroprotective effect remains to be elucidated. In the current proposal it was hypothesized that activation of sigma-1 receptors promotes retinal ganglion cells survival by decreased calcium signaling pathways and factors linked to cell death. We showed by the ratiometric calcium imaging and patch clamp techniques that sigma-1 receptor activation could inhibit both calcium influx and intracellular calcium mobilization. The results showed that sigma-1 receptor overexpressing RGC-5 cells also had a lower glutamate-induced intracellular calcium mobilization compared to non-overexpressing RGC-5 cells. The survival assay data showed that the sigma-1 receptor agonist, (+)-SKF10047 protected RGC-5 cells showed a significant resistance to glutamate-induced apoptosis compared to the control RGC-5 cells. The sigma-1 receptor neuroprotective mechanism also included the down regulation of Bax, and caveolin-1 protein expression levels and inhibited caspase-3 activation. We also demonstrated for the first time using a co-immunoprecipitation technique, the association between L-type calcium channels and sigma-1 receptors. Thus sigma-1 receptor ligands may indirectly influence the voltage-gated calcium channels by interacting with the sigma-1 receptor associated voltage-gated calcium channel complex. In conclusion, activation of sigma-1 receptors can regulate calcium homeostasis and signaling in retinal ganglion cells. Activation of sigma-1 receptors regulate intracellular calcium levels and pro-apoptotic gene expression to promote retinal ganglion cell survival. Sigma-1 receptor ligands may be neuroprotective and targets for potential glaucoma therapeutics.Item Tolerating DNA Damage: Translesion Polymerase ETA (η) and its regulation in Saccharomyces Cerevisiae(2008-05-01) Pabla, Ritu; Siede, Wolfram; Alvarez, Rafael; Reeves, RustinPabla, Ritu., Tolerating DNA damage: Translesion polymerase eta (η) and its regulation in Saccharomyces cerevisiae. Doctor of Philosophy (Cell Biology and Genetics), May 2008, 137 pp., 21 illustrations, bibliography, 151 titles. RAD30 gene encoded DNA polymerase eta (Polη) is the only eukaryotic polymerase that can bypass UV-induced thymine-thymine (T-T) dimers in a predominantly error-free manner. The unique ability of reading bulky and geometrically distorted bases in the template makes the polymerase low-fidelity and error-prone for an undamaged template. The purpose of this study is to delineate the mechanism(s) by which activity of Polη is regulated. The increase in RAD30 transcript after UV damage is not reflected at the protein levels. Instead, Polη is monoubiquitinated constitutively. This posttranslational modification is upregulated in G1 phase and downregulated on entry into S phase of the cell-cycle. This downregulation is further accelerated in response to UV induced DNA damage. A missense mutation (L577Q) of the ubiquitin binding domain (UBZ) results in reduced degree of ubiquitination of the mutant protein outside of G1 and a complete failure to stably interact with ubiquitinated substrates. This mutation renders the strain more UV sensitive and mutagenic, a phenotype resembling a complete RAD30 deletion. In other words, UBZ motif and its interaction with ubiquitinated PCNA is critical for Polη function in vivo. In addition to nucleus, the polymerase localizes in mitochondria suggesting its role in damage tolerance in mitochondria. No drastic changes in the localization of polymerase are observed during cell-cycle progression and after UV damage.Item Translation of Medical Devices: An Assessment of the Common Obstacles Perceived by Clinicians(2010-07-01) Blaylock, Jessica P.; Dr. Patricia GwirtzA medical device is any device used in the treatment or diagnosis of a patient. This practicum project focuses on assessing the process for medical device translation in an academic setting by summarizing the development pathway of medical devices, identifying common obstacles encountered in this pathway, and assessing the clinician’s awareness of the process of medical device translation. This examination was conducted by literature reviews, discussions with professionals, and a clinician survey. Results revealed that successful development of medical devices depends on the cooperation of clinicians and device companies in the coordination of device invention, intellectual property acquisition and regulatory approval. The results indicate that clinicians need to be better educated about medical device research and its hurdles to facilitate medical device development.