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Ni Q, Zhu B, Ji Y, Zheng Q, Liang X, Ma N, Jiang H, Zhang F, Shang Y, Wang Y, Xu S, Zhang E, Yuan Y, Chen T, Yin F, Cao H, Huang J, Xia J, Ding X, Qiu X, Ding K, Song C, Zhou W, Wu M, Wang K, Lui R, Lin Q, Chen W, Li Z, Cheng S, Wang X, Xie D, Li J. PPDPF Promotes the Development of Mutant KRAS-Driven Pancreatic Ductal Adenocarcinoma by Regulating the GEF Activity of SOS1. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2023; 10:e2202448. [PMID: 36453576 PMCID: PMC9839844 DOI: 10.1002/advs.202202448] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Revised: 10/11/2022] [Indexed: 06/17/2023]
Abstract
The guanine nucleotide exchange factor (GEF) SOS1 catalyzes the exchange of GDP for GTP on RAS. However, regulation of the GEF activity remains elusive. Here, the authors report that PPDPF functions as an important regulator of SOS1. The expression of PPDPF is significantly increased in pancreatic ductal adenocarcinoma (PDAC), associated with poor prognosis and recurrence of PDAC patients. Overexpression of PPDPF promotes PDAC cell growth in vitro and in vivo, while PPDPF knockout exerts opposite effects. Pancreatic-specific deletion of PPDPF profoundly inhibits tumor development in KRASG12D -driven genetic mouse models of PDAC. PPDPF can bind GTP and transfer GTP to SOS1. Mutations of the GTP-binding sites severely impair the tumor-promoting effect of PPDPF. Consistently, mutations of the critical amino acids mediating SOS1-PPDPF interaction significantly impair the GEF activity of SOS1. Therefore, this study demonstrates a novel model of KRAS activation via PPDPF-SOS1 axis, and provides a promising therapeutic target for PDAC.
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Križaj D, Cordeiro S, Strauß O. Retinal TRP channels: Cell-type-specific regulators of retinal homeostasis and multimodal integration. Prog Retin Eye Res 2023; 92:101114. [PMID: 36163161 PMCID: PMC9897210 DOI: 10.1016/j.preteyeres.2022.101114] [Citation(s) in RCA: 17] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Revised: 08/03/2022] [Accepted: 08/08/2022] [Indexed: 02/05/2023]
Abstract
Transient receptor potential (TRP) channels are a widely expressed family of 28 evolutionarily conserved cationic ion channels that operate as primary detectors of chemical and physical stimuli and secondary effectors of metabotropic and ionotropic receptors. In vertebrates, the channels are grouped into six related families: TRPC, TRPV, TRPM, TRPA, TRPML, and TRPP. As sensory transducers, TRP channels are ubiquitously expressed across the body and the CNS, mediating critical functions in mechanosensation, nociception, chemosensing, thermosensing, and phototransduction. This article surveys current knowledge about the expression and function of the TRP family in vertebrate retinas, which, while dedicated to transduction and transmission of visual information, are highly susceptible to non-visual stimuli. Every retinal cell expresses multiple TRP subunits, with recent evidence establishing their critical roles in paradigmatic aspects of vertebrate vision that include TRPM1-dependent transduction of ON bipolar signaling, TRPC6/7-mediated ganglion cell phototransduction, TRP/TRPL phototransduction in Drosophila and TRPV4-dependent osmoregulation, mechanotransduction, and regulation of inner and outer blood-retina barriers. TRP channels tune light-dependent and independent functions of retinal circuits by modulating the intracellular concentration of the 2nd messenger calcium, with emerging evidence implicating specific subunits in the pathogenesis of debilitating diseases such as glaucoma, ocular trauma, diabetic retinopathy, and ischemia. Elucidation of TRP channel involvement in retinal biology will yield rewards in terms of fundamental understanding of vertebrate vision and therapeutic targeting to treat diseases caused by channel dysfunction or over-activation.
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Affiliation(s)
- David Križaj
- Departments of Ophthalmology, Neurobiology, and Bioengineering, University of Utah, Salt Lake City, USA
| | - Soenke Cordeiro
- Institute of Physiology, Faculty of Medicine, Christian-Albrechts-University Kiel, Germany
| | - Olaf Strauß
- Experimental Ophthalmology, Department of Ophthalmology, Charité - Universitätsmedizin Berlin, a Corporate Member of Freie Universität, Humboldt-University, The Berlin Institute of Health, Berlin, Germany.
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Smylla TK, Wagner K, Huber A. Application of Fluorescent Proteins for Functional Dissection of the Drosophila Visual System. Int J Mol Sci 2021; 22:8930. [PMID: 34445636 PMCID: PMC8396179 DOI: 10.3390/ijms22168930] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Revised: 08/13/2021] [Accepted: 08/14/2021] [Indexed: 11/22/2022] Open
Abstract
The Drosophila eye has been used extensively to study numerous aspects of biological systems, for example, spatio-temporal regulation of differentiation, visual signal transduction, protein trafficking and neurodegeneration. Right from the advent of fluorescent proteins (FPs) near the end of the millennium, heterologously expressed fusion proteins comprising FPs have been applied in Drosophila vision research not only for subcellular localization of proteins but also for genetic screens and analysis of photoreceptor function. Here, we summarize applications for FPs used in the Drosophila eye as part of genetic screens, to study rhodopsin expression patterns, subcellular protein localization, membrane protein transport or as genetically encoded biosensors for Ca2+ and phospholipids in vivo. We also discuss recently developed FPs that are suitable for super-resolution or correlative light and electron microscopy (CLEM) approaches. Illustrating the possibilities provided by using FPs in Drosophila photoreceptors may aid research in other sensory or neuronal systems that have not yet been studied as well as the Drosophila eye.
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Affiliation(s)
- Thomas K. Smylla
- Department of Biochemistry, Institute of Biology, University of Hohenheim, 70599 Stuttgart, Germany; (K.W.); (A.H.)
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Schopf K, Smylla TK, Huber A. Immunocytochemical Labeling of Rhabdomeric Proteins in Drosophila Photoreceptor Cells Is Compromised by a Light-dependent Technical Artifact. J Histochem Cytochem 2019; 67:745-757. [PMID: 31246149 PMCID: PMC6764007 DOI: 10.1369/0022155419859870] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Drosophila photoreceptor cells are employed as a model system
for studying membrane protein transport. Phototransduction proteins like
rhodopsin and the light-activated TRPL ion channel are transported within the
photoreceptor cell, and they change their subcellular distribution in a
light-dependent way. Investigating the transport mechanisms for rhodopsin and
ion channels requires accurate histochemical methods for protein localization.
By using immunocytochemistry the light-triggered translocation of TRPL has been
described as a two-stage process. In stage 1, TRPL accumulates at the rhabdomere
base and the adjacent stalk membrane a few minutes after onset of illumination
and is internalized in stage 2 by endocytosis after prolonged light exposure.
Here, we show that a commonly observed crescent shaped antibody labeling pattern
suggesting a fast translocation of rhodopsin, TRP, and TRPL to the rhabdomere
base is a light-dependent antibody staining artifact. This artifact is most
probably caused by the profound structural changes in the microvillar membranes
of rhabdomeres that result from activation of the signaling cascade. By using
alternative labeling methods, either eGFP-tags or the self-labeling SNAP-tag, we
show that light activation of TRPL transport indeed results in fast changes of
the TRPL distribution in the rhabdomere but not in the way described
previously.
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Affiliation(s)
- Krystina Schopf
- Department of Biochemistry, Institute of Physiology, University of Hohenheim, Stuttgart, Germany
| | - Thomas K Smylla
- Department of Biochemistry, Institute of Physiology, University of Hohenheim, Stuttgart, Germany
| | - Armin Huber
- Department of Biochemistry, Institute of Physiology, University of Hohenheim, Stuttgart, Germany
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Katz B, Minke B. The Drosophila light-activated TRP and TRPL channels - Targets of the phosphoinositide signaling cascade. Prog Retin Eye Res 2018; 66:200-219. [DOI: 10.1016/j.preteyeres.2018.05.001] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Revised: 04/29/2018] [Accepted: 05/02/2018] [Indexed: 01/28/2023]
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Yasin B, Kohn E, Peters M, Zaguri R, Weiss S, Schopf K, Katz B, Huber A, Minke B. Ectopic Expression of Mouse Melanopsin in Drosophila Photoreceptors Reveals Fast Response Kinetics and Persistent Dark Excitation. J Biol Chem 2017; 292:3624-3636. [PMID: 28119450 PMCID: PMC5339748 DOI: 10.1074/jbc.m116.754770] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2016] [Revised: 01/19/2017] [Indexed: 01/10/2023] Open
Abstract
The intrinsically photosensitive M1 retinal ganglion cells (ipRGC) initiate non-image-forming light-dependent activities and express the melanopsin (OPN4) photopigment. Several features of ipRGC photosensitivity are characteristic of fly photoreceptors. However, the light response kinetics of ipRGC is much slower due to unknown reasons. Here we used transgenic Drosophila, in which the mouse OPN4 replaced the native Rh1 photopigment of Drosophila R1-6 photoreceptors, resulting in deformed rhabdomeric structure. Immunocytochemistry revealed OPN4 expression at the base of the rhabdomeres, mainly at the rhabdomeral stalk. Measurements of the early receptor current, a linear manifestation of photopigment activation, indicated large expression of OPN4 in the plasma membrane. Comparing the early receptor current amplitude and action spectra between WT and the Opn4-expressing Drosophila further indicated that large quantities of a blue absorbing photopigment were expressed, having a dark stable blue intermediate state. Strikingly, the light-induced current of the Opn4-expressing fly photoreceptors was ∼40-fold faster than that of ipRGC. Furthermore, an intense white flash induced a small amplitude prolonged dark current composed of discrete unitary currents similar to the Drosophila single photon responses. The induction of prolonged dark currents by intense blue light could be suppressed by a following intense green light, suggesting induction and suppression of prolonged depolarizing afterpotential. This is the first demonstration of heterologous functional expression of mammalian OPN4 in the genetically emendable Drosophila photoreceptors. Moreover, the fast OPN4-activated ionic current of Drosophila photoreceptors relative to that of mouse ipRGC, indicates that the slow light response of ipRGC does not arise from an intrinsic property of melanopsin.
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Affiliation(s)
- Bushra Yasin
- From the Department of Medical Neurobiology, Institute for Medical Research Israel-Canada (IMRIC) and the Edmond and Lily Safra Center for Brain Sciences (ELSC), Faculty of Medicine, Hebrew University, Jerusalem 91120, Israel and
| | - Elkana Kohn
- From the Department of Medical Neurobiology, Institute for Medical Research Israel-Canada (IMRIC) and the Edmond and Lily Safra Center for Brain Sciences (ELSC), Faculty of Medicine, Hebrew University, Jerusalem 91120, Israel and
| | - Maximilian Peters
- From the Department of Medical Neurobiology, Institute for Medical Research Israel-Canada (IMRIC) and the Edmond and Lily Safra Center for Brain Sciences (ELSC), Faculty of Medicine, Hebrew University, Jerusalem 91120, Israel and
| | - Rachel Zaguri
- From the Department of Medical Neurobiology, Institute for Medical Research Israel-Canada (IMRIC) and the Edmond and Lily Safra Center for Brain Sciences (ELSC), Faculty of Medicine, Hebrew University, Jerusalem 91120, Israel and
| | - Shirley Weiss
- From the Department of Medical Neurobiology, Institute for Medical Research Israel-Canada (IMRIC) and the Edmond and Lily Safra Center for Brain Sciences (ELSC), Faculty of Medicine, Hebrew University, Jerusalem 91120, Israel and
| | - Krystina Schopf
- the Department of Biosensorics, Institute of Physiology, University of Hohenheim, 70599 Stuttgart, Germany
| | - Ben Katz
- From the Department of Medical Neurobiology, Institute for Medical Research Israel-Canada (IMRIC) and the Edmond and Lily Safra Center for Brain Sciences (ELSC), Faculty of Medicine, Hebrew University, Jerusalem 91120, Israel and
| | - Armin Huber
- the Department of Biosensorics, Institute of Physiology, University of Hohenheim, 70599 Stuttgart, Germany
| | - Baruch Minke
- From the Department of Medical Neurobiology, Institute for Medical Research Israel-Canada (IMRIC) and the Edmond and Lily Safra Center for Brain Sciences (ELSC), Faculty of Medicine, Hebrew University, Jerusalem 91120, Israel and
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Schopf K, Huber A. Membrane protein trafficking in Drosophila photoreceptor cells. Eur J Cell Biol 2016; 96:391-401. [PMID: 27964885 DOI: 10.1016/j.ejcb.2016.11.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2016] [Revised: 11/21/2016] [Accepted: 11/28/2016] [Indexed: 10/20/2022] Open
Abstract
Membrane protein trafficking occurs throughout the lifetime of neurons and includes the initial protein synthesis and anterograde transport to the plasma membrane as well as internalization, degradation, and recycling of plasma membrane proteins. Defects in protein trafficking can result in neuronal degeneration and underlie blinding diseases such as retinitis pigmentosa as well as other neuronal disorders. Drosophila photoreceptor cells have emerged as a model system for identifying the components and mechanisms involved in membrane protein trafficking in neurons. Here we summarize the current knowledge about trafficking of three Drosophila phototransduction proteins, the visual pigment rhodopsin and the two light-activated ion channels TRP (transient receptor potential) and TRPL (TRP-like). Despite some common requirements shared by rhodopsin and TRP, details in the trafficking of these proteins differ considerably, suggesting the existence of several trafficking pathways for these photoreceptor proteins.
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Affiliation(s)
- Krystina Schopf
- University of Hohenheim, Institute of Physiology, Department of Biosensorics, Stuttgart, Germany
| | - Armin Huber
- University of Hohenheim, Institute of Physiology, Department of Biosensorics, Stuttgart, Germany.
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