Aberrant activation of Src-family tyrosine kinases (SFKs) directs initiation of metastasis and development of drug resistance in multiple solid tumors and hematological cancers. Since oncogenic mutations of SFKs are rare events, aberrant activation of SFKs in cancer is likely due to dysregulation of the two major upstream inhibitors: C-terminal Src kinase (Csk) and its homolog Csk-homologous kinase (Chk/Matk). Csk and Chk/Matk inhibit SFKs by selectively phosphorylating the inhibitory tyrosine residue at their C-terminal tail. Additionally, Chk/Matk can also employ a non-catalytic inhibitory mechanism to inhibit multiple active forms of SFKs, suggesting that Chk/Matk is a versatile inhibitor capable of constraining the activity of multiple active forms of SFKs. Mounting evidence suggests that Chk/Matk is a potential tumor suppressor downregulated by epigenetic silencing and/or missense mutations in several cancers such as colorectal and lung carcinoma. In spite of the potential significance of Chk/Matk in cancer, little is known about its structure and regulation. This review focuses on the mechanisms by which Chk/Matk expression and activity is downregulated in cancers. Specifically, we assessed the evidence demonstrating downregulation of Chk/Matk by epigenetic silencing and missense mutations in cancers. The other focus is the tumor suppressive mechanism of Chk/Matk. The final focus of the review is on the clinical applications of the investigations into the mechanism of epigenetic silencing of Chk/Matk expression and the tumor suppressive mechanism of Chk/Matk; specifically we discussed how they can benefit the development of biomarkers for early diagnosis of cancers and specific SFK inhibitors for use as cancer therapeutics.
The Hedgehog (Hh) signaling pathway plays crucial roles both in embryonic development and in adult stem cell function. The timing, duration and location of Hh signaling activity need to be tightly controlled. Abnormalities of Hh signal transduction lead to birth defects or malignant tumors. Recent data point to ubiquitination-related posttranslational modifications of several key Hh pathway components as an important mechanism of regulation of the Hh pathway. Here we review how ubiquitination regulates the localization, stability and activity of the key Hh signaling components.
Diabetic nephropathy (DN) is the most common cause of end-stage renal disease (ESRD). About 20%–30% of people with type 1 and type 2 diabetes develop DN . DN is characterized by both glomerulosclerosis with thickening of the glomerular basement membrane and mesangial matrix expansion, and tubulointerstitial fibrosis . Hyperglycemia and the activation of the intra-renal renin-angiotensin system (RAS) in diabetes have been suggested to play a critical role in the pathogenesis of DN. However, the mechanisms are not well known.
Studies from our laboratory demonstrated that the transcription factor—upstream stimulatory factor 2 (USF2) is an important regulator of DN. Moreover, the renin gene is a downstream target of USF2. Importantly, USF2 transgenic (Tg) mice demonstrate a specific increase in renal renin expression and angiotensin II (AngII) levels in kidney and exhibit increased urinary albumin excretion and extracellular matrix deposition in glomeruli, supporting a role for USF2 in the development of diabetic nephropathy. In this review, we summarize our findings of the mechanisms by which diabetes regulates USF2 in kidney cells and its role in regulation of renal renin-angiotensin system and the development of diabetic nephropathy.
The neurotransmitter dopamine acts via two major classes of receptors, D1-type and D2-type. D1 receptors are highly expressed in the striatum and can also be found in the cerebral cortex. Here we review the role of D1 dopamine signaling in two major domains: L-DOPA-induced dyskinesias in Parkinson’s disease and cognition in neuropsychiatric disorders. While there are many drugs targeting D2-type receptors, there are no drugs that specifically target D1 receptors. It has been difficult to use selective D1-receptor agonists for clinical applications due to issues with bioavailability, binding affinity, pharmacological kinetics, and side effects. We propose potential therapies that selectively modulate D1 dopamine signaling by targeting second messengers downstream of D1 receptors, allosteric modulators, or by making targeted modifications to D1-receptor machinery. The development of therapies specific to D1-receptor signaling could be a new frontier in the treatment of neurological and psychiatric disorders.
Neurexins (NRXNs) have been linked to neurodevelopmental and neuropsychiatric disorders and have become attractive drug targets. They are transmembrane neuronal adhesion molecules and play important roles in the formation and differentiation of synapses and synaptic activity. Many postsynaptic binding partners of NRXNs have been identified. The interactions between NRXNs and postsynaptic binding partners can be regulated by alternative splicing, synaptic activity, and RNA binding proteins. The postsynaptic interactive partners may compete with each other for NRXN binding. The expression of NRXNs can also be regulated transcriptionally and post-transcriptionally. Genetic polymorphism may affect the function and expression of NRXNs. In this review, we will summarize the recent advance in these areas. Understanding the biology of neurexin signaling is essential for developing neurexin-based drugs.
With high morbidity and mortality worldwide, tuberculosis (TB) is still an important public health threat. The majority of human TB cases are caused by Mycobacterium tuberculosis. Although pulmonary TB is the most common presentation, M. tuberculosis can disseminate into other organs and causes extrapulmonary TB (EPTB). The dissemination of bacteria from the initial site of infection to other organs can lead to fatal diseases, such as miliary and meningeal TB. Thoroughly understanding the mechanisms and pathways of dissemination would develop therapies to prevent the lethal prognosis of EPTB (miliary and meningeal TB) and vaccines to promote the development of adaptive immunity. This review focuses on risk factors of EPTB, bacterial and host genes involved in EPTB, and potential mechanisms of M. tuberculosis extrapulmonary dissemination.
Neurogenesis persists in two locations of the adult mammalian brain, the subventricular zone of the lateral ventricles and the subgranular zone of the dentate gyrus in the hippocampus. In the adult subgranular zone, radial glial-like cells (RGLs) are multipotent stem cells that can give rise to both astrocytes and neurons. In the process of generating neurons, RGLs divide asymmetrically to give rise to one RGL and one intermediate progenitor cell (IPC). IPCs are considered to be a population of transit amplifying cells that proliferate and eventually give rise to mature granule neurons. The properties of individual IPCs at the clonal level are not well understood. Furthermore, it is not clear whether IPCs can generate astrocytes or revert back to RGLs, besides generating neurons. Here we developed a genetic marking strategy for clonal analysis and lineage-tracing of individual Tbr2-expressing IPCs in the adult hippocampus in vivo using Tbr2-CreERT2 mice. Using this technique we identified Tbr2-CreERT2 labeled IPCs as unipotent neuronal precursors that do not generate astrocytes or RGLs under homeostasis. Additionally, we showed that these labeled IPCs rapidly generate immature neurons in a synchronous manner and do not undergo a significant amount of amplification under homeostasis, in animals subjected to an enriched environment/running, or in animals with different age. In summary, our study suggests that Tbr2-expressing IPCs in the adult mouse hippocampus are unipotent precursors and rapidly give rise to immature neurons without major amplification.
Plant growth is hindered by high concentration of metals in soil by disturbing various physiological processes. However, some bacteria with plant growth promoting features have been recognized to alleviate stress in plants even under elevated levels of metal concentration. The two bacterium NWM 71 and NWM 103, identified as Pseudomonas sp. and Bacillus sp. respectively were found to be resistant to the toxic effects of nickel (Ni2+) and were identified with plant growth promoting features. Both the strains showed the production of indole acetic acid (IAA) and solubilisation of phosphate. Brassica juncea (mustard) was used as a test plant to identify the plant growth promoting activity of the selected strains of bacteria. The growth was positively influenced by the inoculation of both the strains. The tests for the measurement of chlorophyll contents and antioxidative activity were carried out to determine the level of stress in plants. High levels of Ni decreased the growth and chlorophyll content, however, significant increase in the antioxidant activity was recorded along the treatment. Inoculation of both the selected strains of bacteria increased the shoot and root biomass of mustard grown in both unspiked and spiked soil. This positive influence on growth can be attributed to the solubilisation of phosphate and production of IAA. Furthermore the observed high levels of antioxidant enzymes led to decrease in the toxic effects of Ni. This led to enhanced growth and chlorophyll content which in turn might have enhanced the photosynthetic capacity of the plants.
Magnesium–aluminum layered double hydroxide (Mg/Al–LDH) nanoparticles have strong potential application as drug delivery systems because of their low toxicity and suitable biocompatibility. However, few studies have described the morphological effects of these hydroxides on nerve cells. The present study compares the oxidative stress induced by different concentrations (i.e., 0, 50, 100, 200, 400, and 800 μg/mL) of sand flower and flake nano-Mg/Al–LDHs in mouse neuroblastoma cells (N2a) when these cells were exposed for 24 and 48 h. Cell viability was detected by MTT assay, and production of reactive oxygen species (ROS), glutathione (GSH), and malondialdehyde (MDA) were monitored to evaluate oxidative damage. Results suggested that sand flower nano-LDHs, at the appropriate concentrations (less than 200 μg/mL), especially those of about 100–200 nm in size, induce no harmful effects on N2a cells.