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Fulltext Orthosiphon stamineus Proteins Alleviate Pentylenetetrazol-Induced Seizures in Zebrafish

Chung YS, Choo BKM, Ahmed PK, Othman I, Shaikh MF

Biomedicines, 2020 Jul 02;8(7).
PMID: 32630817 DOI: 10.3390/biomedicines8070191

The anticonvulsive potential of proteins extracted from Orthosiphon stamineus leaves (OSLP) has never been elucidated in zebrafish (Danio rerio). This study thus aims to elucidate the anticonvulsive potential of OSLP in pentylenetetrazol (PTZ)-induced seizure model. Physical changes (seizure score and seizure onset time, behavior, locomotor) and neurotransmitter analysis were elucidated to assess the pharmacological activity. The protective mechanism of OSLP on brain was also studied using mass spectrometry-based label-free proteomic quantification (LFQ) and bioinformatics. OSLP was found to be safe up to 800 µg/kg and pre-treatment with OSLP (800 µg/kg, i.p., 30 min) decreased the frequency of convulsive activities (lower seizure score and prolonged seizure onset time), improved locomotor behaviors (reduced erratic swimming movements and bottom-dwelling habit), and lowered the excitatory neurotransmitter (glutamate). Pre-treatment with OSLP increased protein Complexin 2 (Cplx 2) expression in the zebrafish brain. Cplx2 is an important regulator in the trans-SNARE complex which is required during the vesicle priming phase in the calcium-dependent synaptic vesicle exocytosis. Findings in this study collectively suggests that OSLP could be regulating the release of neurotransmitters via calcium-dependent synaptic vesicle exocytosis mediated by the "Synaptic Vesicle Cycle" pathway. OSLP's anticonvulsive actions could be acting differently from diazepam (DZP) and with that, it might not produce the similar cognitive insults such as DZP.

Matched MeSH terms: Exocytosis
Fulltext Annexin II Light Chain p11 Interacts With ENaC to Increase Functional Activity at the Membrane

Cheung TT, Ismail NAS, Moir R, Arora N, McDonald FJ, Condliffe SB

Front Physiol, 2019;10:7.
PMID: 30800070 DOI: 10.3389/fphys.2019.00007

The epithelial Na+ channel (ENaC) provides for Na+ absorption in various types of epithelia including the kidney, lung, and colon where ENaC is localized to the apical membrane to enable Na+ entry into the cell. The degree of Na+ entry via ENaC largely depends on the number of active channels localized to the cell membrane, and is tightly controlled by interactions with ubiquitin ligases, kinases, and G-proteins. While regulation of ENaC endocytosis has been well-studied, relatively little is understood of the proteins that govern ENaC exocytosis. We hypothesized that the annexin II light chain, p11, could participate in the transport of ENaC along the exocytic pathway. Our results demonstrate that all three ENaC channel subunits interacted with p11 in an in vitro binding assay. Furthermore, p11 was able to immunoprecipitate ENaC in epithelial cells. Quantitative mass spectrometry of affinity-purified ENaC-p11 complexes recovered several other trafficking proteins including HSP-90 and annexin A6. We also report that p11 exhibits a robust protein expression in cortical collecting duct epithelial cells. However, the expression of p11 in these cells was not influenced by either short-term or long-term exposure to aldosterone. To determine whether the p11 interaction affected ENaC function, we measured amiloride sensitive Na+ currents in Xenopus oocytes or mammalian epithelia co-expressing ENaC and p11 or a siRNA to p11. Results from these experiments showed that p11 significantly augmented ENaC current, whereas knockdown of p11 decreased current. Further, knockdown of p11 reduced ENaC cell surface population suggesting p11 promotes membrane insertion of ENaC. Overall, our findings reveal a novel protein interaction that controls the number of ENaC channels inserted at the membrane via the exocytic pathway.

Matched MeSH terms: Exocytosis
Glutamate receptors and transporters as comparative cues to the glutamatergic circuits of the avian and mammalian brain

Islam, M.R., Muzaimi, M., Abdullah, J.M.

Orient Neuron Nexus, 2011;2(1):2-9.
MyJurnal

Glutamate is the principal excitatory neurotransmitter in the central nervous system, and plays important roles in both physiological and pathological neuronal processes. Current understanding of the exact mechanisms involved in glutamate-induced neuronal excitotoxicity, in which excessive glutamate causes neuronal dysfunction and degeneration, whether acute or chronic, remain elusive. Conditions, due to acute insults such as ischaemia and traumatic brain injury, and chronic neurodegenerative disorders such as multiple sclerosis and motor neuron disease, suffer from the lack of translational neuroprotection in clinical setting to tackle glutamate excitotoxicity despite steady growth of animal studies that revealed complex cell death pathway interactions. In addition, glutamates are also released by non-neuronal cells including astrocytes and oligodendroglia. Thus, attempts to elucidate this complexity are closely related to our understanding of the glutamatergic circuitry in the brain. Neuronal cells develop a glutamatergic system at glutamatergic synapses that utilise glutamate as an intercellular signaling molecule to characterise the output, input, and termination of this signaling. As to signal input, various kinds of glutamate receptors have been identified and characterized. Na+-dependent glutamate transporters at the plasma membrane are responsible for the signal termination through sequestration of glutamate from the synaptic cleft. The signal output systems comprise vesicular storage and subsequent exocytosis of glutamate by using vesicular glutamate transporters. Similar to the mammalian brain, the regional differences of glutamatergic neurons and glutamate receptor neurons suggest many glutamatergic projections in the avian brain, as supported by recent evidence of glutamate-related genes distribution. Glutamatergic target areas are expected to show high activity of glutamate transporters that remove released glutamate from the synaptic clefts. This review summarises and compares glutamatergic circuits in the avian and mammalian brain, particularly in the olfactory pathway, the paffial organization of glutamatergic neurons and connection with the striatum, hippocampal-septal pathway, visual and auditory pathways, and granule cell-Purkinje cell pathway in the cerebellum. Comparative appreciation of these glutamatergic circuits, particularly with the localisation and/or expression of specific subtypes of glutamate transporters, would provide the morphological basis for physiological and pharmacological designs that supplement existing animal studies of the current proposed mechanisms that underlie glutamate-induced neuronal excitotoxicity.

Matched MeSH terms: Exocytosis
Autophagy and GLUT4: The missing pieces

Elhassan SAM, Candasamy M, Chan EWL, Bhattamisra SK

Diabetes Metab Syndr, 2018 Nov;12(6):1109-1116.
PMID: 29843994 DOI: 10.1016/j.dsx.2018.05.020

BACKGROUND: Autophagy is a process devoted to degrade and recycle cellular components inside mammalian cells through lysosomal system. It plays a main function in the pathophysiology of several diseases. In type 2 diabetes, works demonstrated the dual functions of autophagy in diabetes biology. Studies had approved the role of autophagy in promoting different routes for movement of integral membrane proteins to the plasma membrane. But its role in regulation of GLUT4 trafficking has not been widely observed. In normal conditions, insulin promotes GLUT4 translocation from intracellular membrane compartments to the plasma membrane, while in type 2 diabetes defects occur in this translocation.
METHOD: Intriguing evidences discussed the contribution of different intracellular compartments in autophagy membrane formation. Furthermore, autophagy serves to mobilise membranes within cells, thereby promoting cytoplasmic components reorganisation. The intent of this review is to focus on the possibility of autophagy to act as a carrier for GLUT4 through regulating GLUT4 endocytosis, intracellular trafficking in different compartments, and translocation to cell membrane.
RESULTS: The common themes of autophagy and GLUT4 have been highlighted. The review discussed the overlapping of endocytosis mechanism and intracellular compartments, and has shown that autophagy and GLUT4 utilise similar proteins (SNAREs) which are used for exocytosis. On top of that, PI3K and AMPK also control both autophagy and GLUT4.
CONCLUSION: The control of GLUT4 trafficking through autophagy could be a promising field for treating type 2 diabetes.

Matched MeSH terms: Exocytosis
Fulltext Proteomic Signature of Dysfunctional Circulating Endothelial Colony-Forming Cells of Young Adults

Tan CMJ, Lewandowski AJ, Williamson W, Huckstep OJ, Yu GZ, Fischer R, et al.

J Am Heart Assoc, 2021 Aug 03;10(15):e021119.
PMID: 34275329 DOI: 10.1161/JAHA.121.021119

Background A subpopulation of endothelial progenitor cells called endothelial colony-forming cells (ECFCs) may offer a platform for cellular assessment in clinical studies because of their remarkable angiogenic and expansion potentials in vitro. Despite endothelial cell function being influenced by cardiovascular risk factors, no studies have yet provided a comprehensive proteomic profile to distinguish functional (ie, more angiogenic and expansive cells) versus dysfunctional circulating ECFCs of young adults. The aim of this study was to provide a detailed proteomic comparison between functional and dysfunctional ECFCs. Methods and Results Peripheral blood ECFCs were isolated from 11 subjects (45% men, aged 27±5 years) using Ficoll density gradient centrifugation. ECFCs expressed endothelial and progenitor surface markers and displayed cobblestone-patterned morphology with clonal and angiogenic capacities in vitro. ECFCs were deemed dysfunctional if <1 closed tube formed during the in vitro tube formation assay and proliferation rate was <20%. Hierarchical functional clustering revealed distinct ECFC proteomic signatures between functional and dysfunctional ECFCs with changes in cellular mechanisms involved in exocytosis, vesicle transport, extracellular matrix organization, cell metabolism, and apoptosis. Targeted antiangiogenic proteins in dysfunctional ECFCs included SPARC (secreted protein acidic and rich in cysteine), CD36 (cluster of differentiation 36), LUM (lumican), and PTX3 (pentraxin-related protein PYX3). Conclusions Circulating ECFCs with impaired angiogenesis and expansion capacities have a distinct proteomic profile and significant phenotype changes compared with highly angiogenic endothelial cells. Impaired angiogenesis in dysfunctional ECFCs may underlie the link between endothelial dysfunction and cardiovascular disease risks in young adults.

Matched MeSH terms: Exocytosis
Studies on Plasmodium gallinaceum and Plasmodium juxtanucleare from the Malayan jungle fowl Gallue gallus spadiceus

Fernando MA, Dissanaike AS

Southeast Asian J Trop Med Public Health, 1975 Mar;6(1):25-32.
PMID: 806969
Matched MeSH terms: Exocytosis