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Phorbol Ester Treatment (phorbol_ester + treatment)

Distribution by Scientific Domains

Life Sciences	100%

Selected Abstracts

Overexpression of nPKC , is inhibitory for agrin-induced nicotinic acetylcholine receptor clustering in C2C12 myotubes

JOURNAL OF NEUROSCIENCE RESEARCH, Issue 2 2003
Kathryn Miles
Abstract Protein kinase C (PKC) activity has been implicated in nicotinic acetylcholine receptor (nAChR) cluster disruption but the specific PKC isoforms involved have not been identified. We first tested whether phorbol esters, which activate PKCs, regulate agrin-induced nAChR clustering in C2C12 cells. We found that extended phorbol ester treatment (6 hr) increased nAChR clustering by two-fold. This increase correlated in time with downregulation of PKCs, as indicated by the disappearance of cPKC ,, suggesting that the presence of PKCs is inhibitory for maximal nAChR clustering. To address the question whether nPKC ,, a specific PKC isoform restricted in expression to skeletal muscle and localized to neuromuscular junctions, regulates agrin-induced nAChR cluster formation we overexpressed an nPKC , -green fluorescent protein (GFP) fusion protein in C2C12 myotubes. The number of nAChR clusters was significantly reduced in nPKC ,-GFP compared to GFP overexpressing myotubes at less-than-maximal clustering concentrations of agrin. These data indicate that nPKC , activity inhibits nAChR cluster formation. To examine whether nPKC , activation by phorbol esters regulates agrin-induced nAChR clustering, we treated overexpressing myotubes overnight with maximal agrin concentrations followed by phorbol esters for 1 hr. Phorbol ester treatment reduced preexisting nAChR cluster numbers in nPKC ,-GFP compared to GFP-overexpressing myotubes, suggesting that stimulating nPKC , activity disrupts nAChR clusters in the presence of maximal clustering concentrations of agrin. Together these findings, that nPKC , activity inhibits agrin-induced nAChR cluster formation and disrupts preexisting agrin-induced nAChR clusters, suggest that nPKC , activity is inhibitory for agrin function. © 2002 Wiley-Liss, Inc. [source]

Expression of WASP and Scar1/WAVE1 actin-associated proteins is differentially modulated during differentiation of HL-60 cells

CYTOSKELETON, Issue 4 2003
Sophie Launay
Abstract The Wiskott-Aldrich Syndrome (WAS) is a disease associated with mutations in the WAS gene and characterised by developmental defects in haematopoietic cells such as myeloid cells. The Wiskott-Aldrich Syndrome protein (WASP)-family includes Scar1 and WASP, which are key regulators of actin reorganization in motile cells. To understand the roles of Scar1 and WASP in myeloid cells and their cytoskeletal control in haematopoietic tissues, we have explored their expression during differentiation of the promyeloid cell line HL-60. Undifferentiated HL-60 cells expressed Scar1 and WASP, and differentiation to neutrophils, induced by retinoic acid or non-retinoid agent treatments, led to a decrease in the level of expression of Scar1, whereas WASP expression was unaffected. Differentiation to monocytes/macrophages, induced by phorbol ester treatment, resulted in a decreased expression of both proteins in the adherent mature cells. Vitamin D3 treatment or cytochalasin D in combination with PMA treatment did not affect WASP expression suggesting that adhesion and cytoskeletal integrity were both essential to regulate WASP expression. Scar1 expression was regulated by differentiation, adhesion, and cytoskeletal integrity. Recently, WASP was found to colocalize with actin in the podosomes. In contrast, we show here that Scar1 did not localize with the podosomes in mature monocytes/macrophages. These observations show for the first time that modulation of Scar1 and WASP expression is a component of the differentiation program of myeloid precursors and indicate that WASP and Scar1 have different roles in mature myeloid cells. Cell Motil. Cytoskeleton 54:274,285, 2003. © 2003 Wiley-Liss, Inc. [source]

Enhanced generation of Alzheimer's amyloid-, following chronic exposure to phorbol ester correlates with differential effects on alpha and epsilon isozymes of protein kinase C

JOURNAL OF NEUROCHEMISTRY, Issue 2 2009
Odete A. B. Da Cruz e Silva
Abstract Alzheimer's amyloid precursor protein (APP) sorting and processing are modulated through signal transduction mechanisms regulated by protein phosphorylation. Notably, protein kinase C (PKC) appears to be an important component in signaling pathways that control APP metabolism. PKCs exist in at least 11 conventional and unconventional isoforms, and PKC, and PKC, isoforms have been specifically implicated in controlling the generation of soluble APP and amyloid-, (A,) fragments of APP, although identification of the PKC substrate phospho-state-sensitive effector proteins remains challenging. In the current study, we present evidence that chronic application of phorbol esters to cultured cells in serum-free medium is associated with several phenomena, namely: (i) PKC, down-regulation; (ii) PKC, up-regulation; (iii) accumulation of APP and/or APP carboxyl-terminal fragments in the trans Golgi network; (iv) disappearance of fluorescence from cytoplasmic vesicles bearing a green fluorescent protein tagged form of APP; (v) insensitivity of soluble APP release following acute additional phorbol application; and (vi) elevated cellular APP mRNA levels and holoprotein, and secreted A,. These data indicate that, unlike acute phorbol ester application, which is accompanied by lowered A, generation, chronic phorbol ester treatment causes differential regulation of PKC isozymes and increased A, generation. These data have implications for the design of amyloid-lowering strategies based on modulating PKC activity. [source]