Protein Kinase C - Binding partners and phosphorylation.

Protein Kinase C (PKC) comprises a family of phospholipid-dependent Ser/Thr kinases, implicated in a broad array of cellular processes. PKC activity is subject to a complex network of regulatory inputs, including co-factor binding, phosphorylation and protein-protein interaction. In addition, the chronic activation of PKC frequently leads to its down-regulation this process may be intrinsic to the tumour promoting activity of the phorbol esters. The aim of this work was to investigate the regulation of the novel PKC-e isoform by binding partners and phosphorylation, with a particular focus on the process of agonist-induced degradation. A yeast 2-hybrid screen was performed using a PKC-e bait and two novel binding partners were identified, both with associations to the ubiquitin/proteasome system VHL Binding Protein 1 (VBP1) and F-box WD40 protein 7 (Fbw7). Interactions were verified in mammalian cells and mapped to the catalytic domain of PKC-e. Extensive studies revealed that neither partner influenced the process of PKC-e down-regulation. However, Fbw7a was demonstrated to represent an in vitro PKC substrate. The site of phosphorylation was mapped to Ser-18 and, using phospho-specific antibodies, was shown to be phosphorylated in the cell. PKC-e activity is required for its agonist-induced degradation. Studies were therefore undertaken to investigate autophosphorylation, which may be implicated in this process. Serine residues 234, 316 and 368 were identified as novel PKC-e autophosphorylation sites. Using phospho- specific antibodies, all three sites were shown to be occupied in response to PKC-e activation. Phosphorylation at these sites was found not to influence agonist-induced PKC-e down-regulation. However, a critical role was established for phosphorylated Ser-368, in the recruitment of the PKC-e binding partner, 14-3-3(3. Together these findings provide insight into the mechanisms controlling PKC-e activity and demonstrate a relationship between regulation through phosphorylation and protein-protein interaction

De novo identification of universal cell mechanics regulators

Mechanical proprieties determine many cellular functions, such as cell fate specification, migration, or circulation through vasculature. Identifying factors governing cell mechanical phenotype is therefore a subject of great interest. Here we present a mechanomics approach for establishing links between mechanical phenotype changes and the genes involved in driving them. We employ a machine learning-based discriminative network analysis method termed PC-corr to associate cell mechanical states, measured by real-time deformability cytometry (RT-DC), with large-scale transcriptome datasets ranging from stem cell development to cancer progression, and originating from different murine and human tissues. By intersecting the discriminative networks inferred from two selected datasets, we identify a conserved module of five genes with putative roles in the regulation of cell mechanics. We validate the power of the individual genes to discriminate between soft and stiff cell states in silico, and demonstrate experimentally that the top scoring gene, CAV1, changes the mechanical phenotype of cells when silenced or overexpressed. The data-driven approach presented here has the power of de novo identification of genes involved in cell mechanics regulation and paves the way towards engineering cell mechanical properties on demand to explore their impact on physiological and pathological cell functions

3D correlative light and electron microscopy of cultured cells using serial blockface scanning electron microscopy

The processes of life take place in multiple dimensions, but imaging these processes in even three dimensions is challenging. Here, we describe a workflow for 3D correlative light and electron microscopy (CLEM) of cell monolayers using fluorescence microscopy to identify and follow biological events, combined with serial blockface scanning electron microscopy to analyse the underlying ultrastructure. The workflow encompasses all steps from cell culture to sample processing, imaging strategy, and 3D image processing and analysis. We demonstrate successful application of the workflow to three studies, each aiming to better understand complex and dynamic biological processes, including bacterial and viral infections of cultured cells and formation of entotic cell-in-cell structures commonly observed in tumours. Our workflow revealed new insight into the replicative niche of Mycobacterium tuberculosis in primary human lymphatic endothelial cells, HIV-1 in human monocytederived macrophages, and the composition of the entotic vacuole. The broad application of this 3D CLEM technique will make it a useful addition to the correlative imaging toolbox for biomedical research

Winter wheat in Minnesota

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Tips for profitable small grain production

1 online resource (PDF, 4 pages)This archival publication may not reflect current scientific knowledge or recommendations. Current information available from the University of Minnesota Extension: https://www.extension.umn.edu

Spatial control of Cdc42 signalling by a GM130-RasGRF complex regulates polarity and tumorigenesis

The small GTPase Cdc42 is a key regulator of polarity, but little is known in mammals about its spatial regulation and the relevance of spatial Cdc42 pools for polarity. Here we report the identification of a GM130-RasGRF complex as a regulator of Cdc42 at the Golgi. Silencing GM130 results in RasGRF-dependent inhibition of the Golgi pool of Cdc42, but does not affect Cdc42 at the cell surface. Furthermore, active Cdc42 at the Golgi is important to sustain asymmetric front-rear Cdc42-GTP distribution in directionally migrating cells. Concurrent to Cdc42 inhibition, silencing GM130 also results in RasGRF-dependent Ras-ERK pathway activation. Moreover, depletion of GM130 is sufficient to induce E-cadherin downregulation, indicative of a loss in cell polarity and epithelial identity. Accordingly, GM130 expression is frequently lost in colorectal and breast cancer patients. These findings establish a previously unrecognized role for a GM130-RasGRF-Cdc42 connection in regulating polarity and tumorigenesis

3D correlative light and electron microscopy of cultured cells using serial blockface scanning electron microscopy.

The processes of life take place in multiple dimensions, but imaging these processes in even three dimensions is challenging. Here, we describe a workflow for 3D correlative light and electron microscopy (CLEM) of cell monolayers using fluorescence microscopy to identify and follow biological events, combined with serial blockface scanning electron microscopy to analyse the underlying ultrastructure. The workflow encompasses all steps from cell culture to sample processing, imaging strategy, and 3D image processing and analysis. We demonstrate successful application of the workflow to three studies, each aiming to better understand complex and dynamic biological processes, including bacterial and viral infections of cultured cells and formation of entotic cell-in-cell structures commonly observed in tumours. Our workflow revealed new insight into the replicative niche of Mycobacterium tuberculosis in primary human lymphatic endothelial cells, HIV-1 in human monocyte-derived macrophages, and the composition of the entotic vacuole. The broad application of this 3D CLEM technique will make it a useful addition to the correlative imaging toolbox for biomedical research

Cdc42 Regulates Apical Junction Formation in Human Bronchial Epithelial Cells through PAK4 and Par6B

A systematic screen of Cdc42 targets was carried out in human bronchial epithelial cells. Two kinases, PAK4 and Par6B/aPKC, were identified and are required for maturation of primordial junctions into apical junctions. PAK4 recruitment to primordial junctions is Cdc42-dependent, but maintenance at junctions during maturation is Par6B-dependent

Chemotherapy-induced senescent cancer cells engulf other cells to enhance their survival.

In chemotherapy-treated breast cancer, wild-type p53 preferentially induces senescence over apoptosis, resulting in a persisting cell population constituting residual disease that drives relapse and poor patient survival via the senescence-associated secretory phenotype. Understanding the properties of tumor cells that allow survival after chemotherapy treatment is paramount. Using time-lapse and confocal microscopy to observe interactions of cells in treated tumors, we show here that chemotherapy-induced senescent cells frequently engulf both neighboring senescent or nonsenescent tumor cells at a remarkable frequency. Engulfed cells are processed through the lysosome and broken down, and cells that have engulfed others obtain a survival advantage. Gene expression analysis showed a marked up-regulation of conserved macrophage-like program of engulfment in chemotherapy-induced senescent cell lines and tumors. Our data suggest compelling explanations for how senescent cells persist in dormancy, how they manage the metabolically expensive process of cytokine production that drives relapse in those tumors that respond the worst, and a function for their expanded lysosomal compartment

Identification of New SRF Binding Sites in Genes Modulated by SRF Over-Expression in Mouse Hearts

Background To identify in vivo new cardiac binding sites of serum response factor (SRF) in genes and to study the response of these genes to mild over-expression of SRF, we employed a cardiac-specific, transgenic mouse model, with mild over-expression of SRF (Mild-O SRF Tg). Methodology Microarray experiments were performed on hearts of Mild-O-SRF Tg at 6 months of age. We identified 207 genes that are important for cardiac function that were differentially expressed in vivo. Among them the promoter region of 192 genes had SRF binding motifs, the classic CArG or CArG-like (CArG-L) elements. Fifty-one of the 56 genes with classic SRF binding sites had not been previously reported. These SRF-modulated genes were grouped into 12 categories based on their function. It was observed that genes associated with cardiac energy metabolism shifted toward that of carbohydrate metabolism and away from that of fatty acid metabolism. The expression of genes that are involved in transcription and ion regulation were decreased, but expression of cytoskeletal genes was significantly increased. Using public databases of mouse models of hemodynamic stress (GEO database), we also found that similar altered expression of the SRF-modulated genes occurred in these hearts with cardiac ischemia or aortic constriction as well. Conclusion and significance SRF-modulated genes are actively regulated under various physiological and pathological conditions. We have discovered that a large number of cardiac genes have classic SRF binding sites and were significantly modulated in the Mild-O-SRF Tg mouse hearts. Hence, the mild elevation of SRF protein in the heart that is observed during typical adult aging may have a major impact on many SRF-modulated genes, thereby affecting Cardiac structure and performance. The results from our study could help to enhance our understanding of SRF regulation of cellular processes in the aged heart