| 1. |
- Lönn, Peter, et al.
(författare)
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High-throughput in situ mapping of phosphorylated protein complexes across the cell cycle and in response to drugs
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Interactions and posttranslational modifications (PTMs) of proteins orchestrate cellular responses to cytokines, drugs or other agents, but it has been difficult to monitor and characterize these dynamic events at high-throughput. Here, we have established a semi-automated system for large-scale in situ proximity ligation assays (isPLA). The protocol combines isPLA in microtiter wells with automated microscopy and computer-based image analysis whereby specific protein phosphorylations and interactions are digitally recorded in cells, along with measurements of morphological features. We demonstrate how this platform can improve analysis of cellular signaling by investigating TGF-b responsive Smad2 linker phosphorylations and complex formations over time and across millions of individual cells. We depict single cell responses in relation to e.g. local cell crowding and cell cycle progression via measurements of DNA content and nuclear size. Finally, we illustrate the application of the protocol for demonstrating drug effects by screening a library of phosphatase inhibitors. In summary, our approach expands the scope for image-based single cell analyses by combining observations of protein interactions and modifications with morphological details of individual cells at high throughput.
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| 2. |
- Lönn, Peter, et al.
(författare)
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Image-based high-throughput mapping of TGF-beta-induced phosphocomplexes at a single-cell level
- 2021
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Ingår i: Communications Biology. - : Springer Nature. - 2399-3642. ; 4
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Tidskriftsartikel (refereegranskat)abstract
- To improve our ability to monitor cellular responses to e.g. cytokines or drugs, Lonn et al have developed a semi-automated system for large-scale in situ proximity ligation assays (isPLA) in HaCAT keratinocyte cells. Their approach expands the scope for image-based single cell analyses by combining observations of protein interactions and modifications with morphological details of individual cells at high throughput. Protein interactions and posttranslational modifications orchestrate cellular responses to e.g. cytokines and drugs, but it has been difficult to monitor these dynamic events in high-throughput. Here, we describe a semi-automated system for large-scale in situ proximity ligation assays (isPLA), combining isPLA in microtiter wells with automated microscopy and computer-based image analysis. Phosphorylations and interactions are digitally recorded along with subcellular morphological features. We investigated TGF-beta-responsive Smad2 linker phosphorylations and complex formations over time and across millions of individual cells, and we relate these events to cell cycle progression and local cell crowding via measurements of DNA content and nuclear size of individual cells, and of their relative positions. We illustrate the suitability of this protocol to screen for drug effects using phosphatase inhibitors. Our approach expands the scope for image-based single cell analyses by combining observations of protein interactions and modifications with morphological details of individual cells at high throughput.
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| 3. |
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| 4. |
- Barkefors, Irmeli, et al.
(författare)
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Exocyst Complex Component 3-like 2 (EXOC3L2) Associates with the Exocyst Complex and Mediates Directional Migration of Endothelial Cells
- 2011
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 286:27, s. 24189-24199
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Tidskriftsartikel (refereegranskat)abstract
- The exocyst is a protein complex that ensures spatial targeting of exocytotic vesicles to the plasma membrane. We present microarray data obtained from differentiating mouse embryonic stem cell cultures that identify an up-regulation of exocyst complex component 3-like 2 (exoc3l2) mRNA in sprouting blood vessels. Vascular expression of exoc3l2 is confirmed by qPCR analysis of different mouse tissues and immunofluorescence analyses of mouse brain sections. We detect an up-regulation of exoc3l2 mRNA synthesis in primary human endothelial cells in response to VEGFA, and this response is enhanced when the cells are grown on a three-dimensional collagen I matrix. Myc-tagged EXOC3L2 co-precipitates with the exocyst protein EXOC4, and immunofluorescence detection of EXOC3L2 shows partial subcellular colocalization with EXOC4 and EXOC7. Finally, we show that exoc3l2 silencing inhibits VEGF receptor 2 phosphorylation and VEGFA-directed migration of cultured endothelial cells.
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| 5. |
- Blom, Magdalena, et al.
(författare)
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The atypical Rho GTPase RhoD is a regulator of actin cytoskeleton dynamics and directed cell migration
- 2017
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Ingår i: Experimental Cell Research. - : Elsevier BV. - 0014-4827 .- 1090-2422. ; 352:2, s. 255-264
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Tidskriftsartikel (refereegranskat)abstract
- RhoD belongs to the Rho GTPases, a protein family responsible for the regulation and organization of the actin cytoskeleton, and, consequently, many cellular processes like cell migration, cell division and vesicle trafficking. Here, we demonstrate that the actin cytoskeleton is dynamically regulated by increased or decreased protein levels of RhoD. Ectopic expression of RhoD has previously been shown to give an intertwined weave of actin filaments. We show that this RhoD-dependent effect is detected in several cell types and results in a less dynamic actin filament system. In contrast, RhoD depletion leads to increased actin filament-containing structures, such as cortical actin, stress fibers and edge ruffles. Moreover, vital cellular functions such as cell migration and proliferation are defective when RhoD is silenced. Taken together, we present data suggesting that RhoD is an important component in the control of actin dynamics and directed cell migration.
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| 6. |
- Heldin, Johan, et al.
(författare)
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Dynamin inhibitors impair platelet-derived growth factor beta-receptor dimerization and signaling
- 2019
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Ingår i: Experimental Cell Research. - : ELSEVIER INC. - 0014-4827 .- 1090-2422. ; 380:1, s. 69-79
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Tidskriftsartikel (refereegranskat)abstract
- The role of plasma membrane composition and dynamics in the activation process of receptor tyrosine kinases (RTKs) is still poorly understood. In this study we have investigated how signaling via the RTK, platelet-derived growth factor beta-receptor (PDGFR-beta) is affected by Dynasore or Dyngo-4a, which are commonly used dynamin inhibitors. PDGFR-beta preferentially internalizes via clathrin-coated pits and in this pathway, Dynamin II has a major role in the formation and release of vesicles from the plasma membrane by performing the membrane scission. We have found that dynamin inhibitors impedes the activation of PDGFR-beta by impairing ligand-induced dimerization of the receptor monomers, which leads to a subsequent lack of phosphorylation and activation both of receptors and downstream effectors, such as ERK1/2 and AKT. In contrast, dynamin inhibitors did not affect epidermal growth factor receptor (EGFR) dimerization and phosphorylation. Our findings suggest that there is a link between plasma membrane dynamics and PDGFR-beta activation, and that this link is not shared with the epidermal growth factor receptor.
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| 7. |
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| 8. |
- Heldin, Johan, et al.
(författare)
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FGD5 sustains vascular endothelial growth factor A (VEGFA) signaling through inhibition of proteasome-mediated VEGF receptor 2 degradation
- 2017
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Ingår i: Cellular Signalling. - : Elsevier BV. - 0898-6568 .- 1873-3913. ; 40, s. 125-132
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Tidskriftsartikel (refereegranskat)abstract
- The complete repertoire of endothelial functions elicited by FGD5, a guanine nucleotide exchange factor activating the Rho GTPase Cdc42, has yet to be elucidated. Here we explore FGD5's importance during vascular endothelial growth factor A (VEGFA) signaling via VEGF receptor 2 (VEGFR2) in human endothelial cells. In microvascular endothelial cells, FGD5 is located at the inner surface of the cell membrane as well as at the outer surface of EEAl-positive endosomes carrying VEGFR2. The latter finding prompted us to explore if FGD5 regulates VEGFR2 dynamics. We found that depletion of FGD5 in microvascular cells inhibited their migration towards a stable VEGFA gradient. Furthermore, depletion of FGD5 resulted in accelerated VEGFR2 degradation, which was reverted by lactacystin-mediated proteasomal inhibition. Our results thus suggest a mechanism whereby FGD5 sustains VEGFA signaling and endothelial cell chemotaxis via inhibition of proteasome-dependent VEGFR2 degradation.
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| 9. |
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| 10. |
- Heldin, Johan
(författare)
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Identification and Characterization of Proteins and MicroRNAs that Modulate Receptor Signaling, Vesicular Trafficking and Cell Migration in Vascular Cells
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Blood vessels deliver nutrients and oxygen to tissues. Importantly, the functions and growth of blood vessels are commonly altered in disease. The inside of all blood vessels are lined with endothelium, a thin specialized layer of endothelial cells that separate the blood from other tissues. This thesis deals with the identification and functional characterization of proteins and microRNAs that have key roles as modulators of growth factor signaling and directed cell migration of endothelial cells and other vascular cells.A previously uncharacterized protein of the exocyst complex, Exocyst complex component 3-like 2 (ExoC3L2) was identified and shown to be highly expressed in endothelial cells of sprouting vessels. Suppression of ExoC3L2 resulted in reduced VEGF-A signaling together with reduced chemotaxis in response to VEGF-A gradients. VEGF-A-signaling via its receptor VEGFR-2 is thus modulated by the exocyst complex and ExoC3L2.Expression profiling of highly vascularized tissues were used to identify several microRNAs selectively expressed in blood vessels. miR-145, targeting the transcription factor Fli1, was shown to be expressed in pericytes and mural cells. Elevated levels of miR-145 reduced chemotaxis of both endothelial cells and fibroblasts in response to growth factor gradients. miR-145 depletion in fibroblasts was shown to inhibit chemotaxis in response to PDGF-BB.The guanine nucleotide exchange factor FGD5 was shown to be selectively expressed in endothelial cells and to regulate Cdc42 activity. FGD5 was shown to regulate the turnover of activated VEGF-receptors. Suppression of FGD5 impaired endothelial cell chemotaxis, suggesting that FGD5 is required for efficient and sustained VEGF-A signaling.Inactivation of RhoD, a regulator of endosomal trafficking, resulted in an increased pool of acetylated and stable microtubules. Knockdown of RhoD in human fibroblasts resulted in a loss of cell polarity. A link between PDGFR-β and RhoD was implicated by the finding that PDGF-BB was shown to trigger formation of GTP-bound RhoD. Chemotaxis towards PDGF-BB was severely inhibited in cells with reduced RhoD expression, suggesting a role for RhoD in chemotaxis via its regulation of microtubule dynamics.
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