Voltage-Gated Potassium Channels as Regulators of Cell Death

Ion channels allow the flux of specific ions across biological membranes, thereby determining ion homeostasis within the cells. Voltage-gated potassium-selective ion channels crucially contribute to the setting of the plasma membrane potential, to volume regulation and to the physiologically relevant modulation of intracellular potassium concentration. In turn, these factors affect cell cycle progression, proliferation and apoptosis. The present review summarizes our current knowledge about the involvement of various voltage-gated channels of the Kv family in the above processes and discusses the possibility of their pharmacological targeting in the context of cancer with special emphasis on Kv1.1, Kv1.3, Kv1.5, Kv2.1, Kv10.1, and Kv11.1.

Gamma-Tocotrienol Stimulates the Proliferation, Differentiation, and Mineralization in Osteoblastic MC3T3-E1 Cells

Gamma-tocotrienol, a major component of tocotrienol-rich fraction of palm oil, has been suggested to exhibit bone protective effectsin vivo. However, the effects ofγ-tocotrienol on osteoblast cells are still unclear. In this study, the effects ofγ-tocotrienol on the proliferation, differentiation, and mineralization in osteoblastic MC3T3-E1 cells were investigated. Our results showed thatγ-tocotrienol (2–8 μmol/L) significantly improved the cell proliferation (p<0.05), but it did not affect cell cycle progression.γ-Tocotrienol significantly increased alkaline phosphatase (ALP) activity (p<0.05), secretion levels of osteocalcin (OC) and osteonectin (ON), and mRNA levels of collagen type I (Col I) of MC3T3-E1 cells. Meanwhile, we found thatγ-tocotrienol is promoted in differentiation MC3T3-E1 cells by upregulation of the expression of Runx2 protein. Moreover, the number of bone nodules increased over 2.5-fold in cells treated withγ-tocotrienol (2–8 μmol/L) for 24 d compared to control group. These results indicated thatγ-tocotrienol at low dose levels, especially 4 μmol/L, could markedly enhance the osteoblastic function by increasing the proliferation, differentiation, and mineralization of osteoblastic MC3T3-E1 cells. Moreover, our data also indicated that Runx2 protein may be involved in these effects. Further studies are needed to determine the potential ofγ-tocotrienol as an antiosteoporotic agent.

Design, Synthesis, Antitumor activity, cell cycle analysis and ELISA assay for Cyclin Dependant Kinase-2 of a new (4-aryl-6-flouro-4H-benzo[4, 5] thieno[3, 2-b] pyran) derivatives.

A series of benzo[b]thiophene and their benzo[4,5]thieno[3,2-b]pyran derivatives (3a-f), (4a-f), (5a-f) and 6 were synthesized and characterized by spectroscopic and elemental analysis. All compounds were subjected to one dose anticancer screening in NCI- America, but only the compounds gave high percent growth inhibition were further subjected to five dose screening. A good result of compound 4f with GI50 = 0.15 µmol, TGI= 1.14 µmol and 4c with GI50 = 1.09 µmol, TGI = 10.19 µmol, LC50 = 100 µmol on HT-29 cell line. To explore mechanism of cytotoxicity, compound 4f and 4c were allowed to affect cell cycle progression using HT-29 cell line (human colon cancer) in two-time interval (24 and 48 hr). The cytotoxicity of 4f and 4c was correlated with induction of apoptosis causing pre-G1apoptosis and cell growth arrest at G2/M in a time dependant manner through inhibition of CDK-2. For exploring the SAR for all synthesized compounds, IC50 of 5d was determined which was equal to 0.32 ±0.05 µmol, IC50 of 6 was equal to be 0.15 ±0.01 µmol while IC50 of erlotinib reference was equal to 0.3±0.02 µmol. Finally we were able to synthesize a series of benzo[b] thiophene, benzo[4,5]thieno[3,2-b]pyran having a good cytotoxic activity suggesting promising anticancer derivatives.

ID: 90: ADAM10 REGULATES STEMNESS OF ADULT NEURAL STEM CELLS BY MEDIATING THEIR POSITIONING WITHIN THE SVZ NICHE

The subventricular zone (SVZ) niche has been defined to have two distinct microenivroments, an apical compartment that is directly in contact with CSF and a basal compartment with a rich vascular network. Both these compartments regulate neural stem cell (NSC) properties via a diverse array of extrinsic cues by regulating both NSC-NSC and NSC-niche interactions. A majority of these signaling mechanisms are initiated by metalloproteinases. In this study, we investigated one such molecule, a disintegrin and metalloproteinase 10 (ADAM10) and its role in maintaining NSC properties. Using a conditional knockout, in which ADAM10 is specifically deleted in NSCs and NPCs (Nestin-CRE™/ADAM10fl/fl; denoted as KO) we noted altered contacts within the apical and basal compartments. BrdU pulse-chase studies demonstrated an increased number of long-term retaining BrdU NSCs in these KO mice. We also observed decreased BrdU label retaining neurons in the olfactory bulb in addition to a decreased neuroblast population in the SVZ indicating impaired neurogenesis in the KO mice. Intriguingly, we also observed cytoskeletal changes in NSCs and decreased migration of cells from the core of neurospheres derived from KO SVZ cells. This altered cell shape could intrinsically affect cell cycle progression. Taken together, this data suggests ADAM10 activity within the SVZ niche regulates NSC intrinsic properties and alters their cell cycle progression. Moreover, ADAM10 deletion appears to promote an aberrant self-renewal phenotype in NSCs preventing their differentiation. A more thorough understanding of how ADAM10 mediates these cellular changes and the underlying molecular mechanisms could be crucial in enhancing SVZ neurogenesis.

Putting the model to the test: are APC proteins essential for neuronal polarity, axon outgrowth, and axon targeting?

The highly polarized architecture of neurons is important for their function. Experimental data based on dominant-negative approaches suggest that the tumor suppressor adenomatous polyposis coli (APC), a regulator of Wnt signaling and the cytoskeleton, regulates polarity of neuroectodermal precursors and neurons, helping specify one neurite as the axon, promoting its outgrowth, and guiding axon pathfinding. However, such dominant-negative approaches might affect processes in which APC is not essential. We completely removed both APCs from Drosophila melanogaster larval neural precursors and neurons, testing whether APCs play universal roles in neuronal polarity. Surprisingly, APCs are not essential for asymmetric cell division or the stereotyped division axis of central brain (CB) neuroblasts, although they do affect cell cycle progression and spindle architecture. Likewise, CB, lobular plug, and mushroom body neurons do not require APCs for polarization, axon outgrowth, or, in the latter two cases, axon targeting. These data suggest that proposed cytoskeletal roles for APCs in mammals should be reassessed using loss of function tools.

LKB1 induces apical trafficking of Silnoon, a monocarboxylate transporter, in Drosophila melanogaster

Silnoon (Sln) is a monocarboxylate transporter (MCT) that mediates active transport of metabolic monocarboxylates such as butyrate and lactate. Here, we identify Sln as a novel LKB1-interacting protein using Drosophila melanogaster genetic modifier screening. Sln expression does not affect cell cycle progression or cell size but specifically enhances LKB1-dependent apoptosis and tissue size reduction. Conversely, down-regulation of Sln suppresses LKB1-dependent apoptosis, implicating Sln as a downstream mediator of LKB1. The kinase activity of LKB1 induces apical trafficking of Sln in polarized cells, and LKB1-dependent Sln trafficking is crucial for triggering apoptosis induced by extracellular butyrate. Given that LKB1 functions to control both epithelial polarity and cell death, we propose Sln is an important downstream target of LKB1.