1
|
Melrose J. Dystroglycan-HSPG interactions provide synaptic plasticity and specificity. Glycobiology 2024; 34:cwae051. [PMID: 39223703 PMCID: PMC11368572 DOI: 10.1093/glycob/cwae051] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2024] [Accepted: 07/10/2024] [Indexed: 09/04/2024] Open
Abstract
AIM This study examined the roles of the laminin and proteoglycan receptor dystroglycan (DG) in extracellular matrix stabilization and cellular mechanosensory processes conveyed through communication between the extracellular matrix (ECM) and cytoskeleton facilitated by DG. Specific functional attributes of HS-proteoglycans (HSPGs) are conveyed through interactions with DG and provide synaptic specificity through diverse interactions with an extensive range of cell attachment and adaptor proteins which convey synaptic plasticity. HSPG-DG interactions are important in phototransduction and neurotransduction and facilitate retinal bipolar-photoreceptor neuronal signaling in vision. Besides synaptic stabilization, HSPG-DG interactions also stabilize basement membranes and the ECM and have specific roles in the assembly and function of the neuromuscular junction. This provides neuromuscular control of muscle systems that control conscious body movement as well as essential autonomic control of diaphragm, intercostal and abdominal muscles and muscle systems in the face, mouth and pharynx which assist in breathing processes. DG is thus a multifunctional cell regulatory glycoprotein receptor and regulates a diverse range of biological and physiological processes throughout the human body. The unique glycosylation of the αDG domain is responsible for its diverse interactions with ECM components in cell-ECM signaling. Cytoskeletal cell regulatory switches assembled by the βDG domain in its role as a nuclear scaffolding protein respond to such ECM cues to regulate cellular behavior and tissue homeostasis thus DG has fascinating and diverse roles in health and disease.
Collapse
Affiliation(s)
- James Melrose
- Raymond Purves Bone and Joint Research Laboratory, Kolling Institute, St. Leonards, NSW 2065, Australia
- School of Medical Sciences, Faculty of Medicine and Health, The University of Sydney at Royal North Shore Hospital, St. Leonards, NSW 2065, Australia
- Graduate School of Biomedical Engineering, Faculty of Engineering, University of New South Wales, Sydney, NSW 2052, Australia
| |
Collapse
|
2
|
Melrose J. CNS/PNS proteoglycans functionalize neuronal and astrocyte niche microenvironments optimizing cellular activity by preserving membrane polarization dynamics, ionic microenvironments, ion fluxes, neuronal activation, and network neurotransductive capacity. J Neurosci Res 2024; 102:e25361. [PMID: 39034899 DOI: 10.1002/jnr.25361] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2023] [Revised: 03/22/2024] [Accepted: 05/27/2024] [Indexed: 07/23/2024]
Abstract
Central and peripheral nervous system (CNS/PNS) proteoglycans (PGs) have diverse functional roles, this study examined how these control cellular behavior and tissue function. The CNS/PNS extracellular matrix (ECM) is a dynamic, responsive, highly interactive, space-filling, cell supportive, stabilizing structure maintaining tissue compartments, ionic microenvironments, and microgradients that regulate neuronal activity and maintain the neuron in an optimal ionic microenvironment. The CNS/PNS contains a high glycosaminoglycan content (60% hyaluronan, HA) and a diverse range of stabilizing PGs. Immobilization of HA in brain tissues by HA interactive hyalectan PGs preserves tissue hydration and neuronal activity, a paucity of HA in brain tissues results in a pro-convulsant epileptic phenotype. Diverse CS, KS, and HSPGs stabilize the blood-brain barrier and neurovascular unit, provide smart gel neurotransmitter neuron vesicle storage and delivery, organize the neuromuscular junction basement membrane, and provide motor neuron synaptic plasticity, and photoreceptor and neuron synaptic functions. PG-HA networks maintain ionic fluxes and microgradients and tissue compartments that contribute to membrane polarization dynamics essential to neuronal activation and neurotransduction. Hyalectans form neuroprotective perineuronal nets contributing to synaptic plasticity, memory, and cognitive learning. Sialoglycoprotein associated with cones and rods (SPACRCAN), an HA binding CSPG, stabilizes the inter-photoreceptor ECM. HSPGs pikachurin and eyes shut stabilize the photoreceptor synapse aiding in phototransduction and neurotransduction with retinal bipolar neurons crucial to visual acuity. This is achieved through Laminin G motifs in pikachurin, eyes shut, and neurexins that interact with the dystroglycan-cytoskeleton-ECM-stabilizing synaptic interconnections, neuronal interactive specificity, and co-ordination of regulatory action potentials in neural networks.
Collapse
Affiliation(s)
- James Melrose
- Raymond Purves Bone and Joint Research Laboratory, Kolling Institute, Northern Sydney Local Health District, St. Leonards, New South Wales, Australia
- Graduate School of Biomedical Engineering, University of New South Wales, Sydney, New South Wales, Australia
- Sydney Medical School, Northern, The University of Sydney Faculty of Medicine and Health, Royal North Shore Hospital, St. Leonards, New South Wales, Australia
| |
Collapse
|
3
|
Miller ML, Pindwarawala M, Agosto MA. Complex N-glycosylation of mGluR6 is required for trans-synaptic interaction with ELFN adhesion proteins. J Biol Chem 2024; 300:107119. [PMID: 38428819 PMCID: PMC10973816 DOI: 10.1016/j.jbc.2024.107119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2023] [Revised: 01/30/2024] [Accepted: 02/16/2024] [Indexed: 03/03/2024] Open
Abstract
Synaptic transmission from retinal photoreceptors to downstream ON-type bipolar cells (BCs) depends on the postsynaptic metabotropic glutamate receptor mGluR6, located at the BC dendritic tips. Glutamate binding to mGluR6 initiates G-protein signaling that ultimately leads to BC depolarization in response to light. The mGluR6 receptor also engages in trans-synaptic interactions with presynaptic ELFN adhesion proteins. The roles of post-translational modifications in mGluR6 trafficking and function are unknown. Treatment with glycosidase enzymes PNGase F and Endo H demonstrated that both endogenous and heterologously expressed mGluR6 contain complex N-glycosylation acquired in the Golgi. Pull-down experiments with ELFN1 and ELFN2 extracellular domains revealed that these proteins interact exclusively with the complex glycosylated form of mGluR6. Mutation of the four predicted N-glycosylation sites, either singly or in combination, revealed that all four sites are glycosylated. Single mutations partially reduced, but did not abolish, surface expression in heterologous cells, while triple mutants had little or no surface expression, indicating that no single glycosylation site is necessary or sufficient for plasma membrane trafficking. Mutation at N445 severely impaired both ELFN1 and ELFN2 binding. All single mutants exhibited dendritic tip enrichment in rod BCs, as did the triple mutant with N445 as the sole N-glycosylation site, demonstrating that glycosylation at N445 is sufficient but not necessary for dendritic tip localization. The quadruple mutant was completely mislocalized. These results reveal a key role for complex N-glycosylation in regulating mGluR6 trafficking and ELFN binding, and by extension, function of the photoreceptor synapses.
Collapse
Affiliation(s)
- Michael L Miller
- Faculty of Science, Medical Sciences Program, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Mustansir Pindwarawala
- Faculty of Science, Medical Sciences Program, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Melina A Agosto
- Retina and Optic Nerve Research Laboratory, Dalhousie University, Halifax, Nova Scotia, Canada; Department of Physiology and Biophysics, Dalhousie University, Halifax, Nova Scotia, Canada; Department of Ophthalmology and Visual Sciences, Dalhousie University, Halifax, Nova Scotia, Canada.
| |
Collapse
|
4
|
Wakeham CM, Shi Q, Ren G, Haley TL, Duvoisin RM, von Gersdorff H, Morgans CW. Trophoblast glycoprotein is required for efficient synaptic vesicle exocytosis from retinal rod bipolar cells. Front Cell Neurosci 2023; 17:1306006. [PMID: 38099150 PMCID: PMC10720453 DOI: 10.3389/fncel.2023.1306006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2023] [Accepted: 11/02/2023] [Indexed: 12/17/2023] Open
Abstract
Introduction Rod bipolar cells (RBCs) faithfully transmit light-driven signals from rod photoreceptors in the outer retina to third order neurons in the inner retina. Recently, significant work has focused on the role of leucine-rich repeat (LRR) proteins in synaptic development and signal transduction at RBC synapses. We previously identified trophoblast glycoprotein (TPBG) as a novel transmembrane LRR protein localized to the dendrites and axon terminals of RBCs. Methods We examined the effects on RBC physiology and retinal processing of TPBG genetic knockout in mice using immunofluorescence and electron microscopy, electroretinogram recording, patch-clamp electrophysiology, and time-resolved membrane capacitance measurements. Results The scotopic electroretinogram showed a modest increase in the b-wave and a marked attenuation in oscillatory potentials in the TPBG knockout. No effect of TPBG knockout was observed on the RBC dendritic morphology, TRPM1 currents, or RBC excitability. Because scotopic oscillatory potentials primarily reflect RBC-driven rhythmic activity of the inner retina, we investigated the contribution of TPBG to downstream transmission from RBCs to third-order neurons. Using electron microscopy, we found shorter synaptic ribbons in TPBG knockout axon terminals in RBCs. Time-resolved capacitance measurements indicated that TPBG knockout reduces synaptic vesicle exocytosis and subsequent GABAergic reciprocal feedback without altering voltage-gated Ca2+ currents. Discussion TPBG is required for normal synaptic ribbon development and efficient neurotransmitter release from RBCs to downstream cells. Our results highlight a novel synaptic role for TPBG at RBC ribbon synapses and support further examination into the mechanisms by which TPBG regulates RBC physiology and circuit function.
Collapse
Affiliation(s)
- Colin M. Wakeham
- Department of Chemical Physiology and Biochemistry, Oregon Health and Science University, Portland, OR, United States
| | - Qing Shi
- Department of Chemical Physiology and Biochemistry, Oregon Health and Science University, Portland, OR, United States
| | - Gaoying Ren
- Department of Chemical Physiology and Biochemistry, Oregon Health and Science University, Portland, OR, United States
| | - Tammie L. Haley
- Department of Chemical Physiology and Biochemistry, Oregon Health and Science University, Portland, OR, United States
| | - Robert M. Duvoisin
- Department of Chemical Physiology and Biochemistry, Oregon Health and Science University, Portland, OR, United States
| | - Henrique von Gersdorff
- Department of Chemical Physiology and Biochemistry, Oregon Health and Science University, Portland, OR, United States
- Vollum Institute, Oregon Health and Science University, Portland, OR, United States
- Casey Eye Institute, Oregon Health and Science University, Portland, OR, United States
| | - Catherine W. Morgans
- Department of Chemical Physiology and Biochemistry, Oregon Health and Science University, Portland, OR, United States
| |
Collapse
|
5
|
Zhang J, Meng X, Zhou Y, Jiang Z, Chen H, Meng Z, Zhang Q, Chen W. Lnc-LRRTM4 promotes proliferation, metastasis and EMT of colorectal cancer through activating LRRTM4 transcription. Cancer Cell Int 2023; 23:142. [PMID: 37468908 DOI: 10.1186/s12935-023-02986-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2023] [Accepted: 07/05/2023] [Indexed: 07/21/2023] Open
Abstract
Numerous mechanisms have shown that long noncoding RNAs (lncRNAs) promote the development of colorectal cancer (CRC), but the role of lnc-LRRTM4 in the progression of CRC remains unclear. In this article, we found that lnc-LRRTM4 was highly expressed in CRC tissues and cell lines and that lnc-LRRTM4 could promote the proliferation and metastasis of CRC cells. These consequences were achieved by lnc-LRRTM4 directly binding to the promoter of LRRTM4 to induce its transcription. Moreover, lnc-LRRTM4 enhanced the growth of CRC cells in vivo by promoting cell cycle progression and reducing apoptosis. Taken together, our results revealed that lnc-LRRTM4 promotes the proliferation and metastasis of CRC cells, suggesting that it may be a potential diagnostic and therapeutic target for CRC.
Collapse
Affiliation(s)
- Jingjie Zhang
- Department of Gastroenterology, The First Affiliated Hospital of Soochow University, Suzhou, 215000, Jiangsu, P. R. China
- Center of Digestive Endoscopy, The Second Affiliated Hospital of Baotou Medical College, Baotou, 014000, Inner Mongolia, China
| | - Xianmei Meng
- Center of Digestive Endoscopy, The Second Affiliated Hospital of Baotou Medical College, Baotou, 014000, Inner Mongolia, China
| | - Yi Zhou
- Center of Digestive Endoscopy, The Second Affiliated Hospital of Baotou Medical College, Baotou, 014000, Inner Mongolia, China
| | - Zhengyu Jiang
- Center of Digestive Endoscopy, The Second Affiliated Hospital of Baotou Medical College, Baotou, 014000, Inner Mongolia, China
| | - Hongsuo Chen
- Center of Digestive Endoscopy, The Second Affiliated Hospital of Baotou Medical College, Baotou, 014000, Inner Mongolia, China
| | - Zhiyi Meng
- Center of Digestive Endoscopy, The Second Affiliated Hospital of Baotou Medical College, Baotou, 014000, Inner Mongolia, China
| | - Qi Zhang
- Department of Gastroenterology, The First Affiliated Hospital of Soochow University, Suzhou, 215000, Jiangsu, P. R. China
- Department of Gastroenterology, The Affiliated Hospital of Xuzhou Medical University, Xuzhou, 221000, Jiangsu, China
| | - Weichang Chen
- Department of Gastroenterology, The First Affiliated Hospital of Soochow University, Suzhou, 215000, Jiangsu, P. R. China.
| |
Collapse
|
6
|
Gregg RG, Hasan N, Borghuis BG. LRIT3 expression in cone photoreceptors restores post-synaptic bipolar cell signalplex assembly and partial function in Lrit3 -/- mice. iScience 2023; 26:106499. [PMID: 37091241 PMCID: PMC10113827 DOI: 10.1016/j.isci.2023.106499] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Revised: 12/20/2022] [Accepted: 03/22/2023] [Indexed: 04/25/2023] Open
Abstract
Complete congenital stationary night blindness (cCSNB) is a heterogeneous disorder characterized by poor dim-light vision, myopia, and nystagmus that is caused by mutations in genes critical for signal transmission between photoreceptors and depolarizing bipolar cells (DBCs). One such gene, LRIT3, is required for assembly of the post-synaptic signaling complex (signalplex) at the dendritic tips of DBCs, although the number of signalplex components impacted is greater in cone DBCs (all components) than in rod bipolar cells (only TRPM1 and Nyctalopin). Here we show that rAAV-mediated expression of LRIT3 in cones results in robust rescue of cone DBC signalplex components and partially restores downstream visual function, as measured by the light-adapted electroretinogram (ERG) b-wave and electrophysiological recordings of bipolar cells (BCs) and RGCs. These data show that LRIT3 successfully restores partial function to cone DBCs most likely in a trans-synaptic manner, potentially paving the way for therapeutic intervention in LRIT3-associated cCSNB.
Collapse
Affiliation(s)
- Ronald G. Gregg
- Department of Biochemistry and Molecular Genetics, University of Louisville, Louisville, KY 40292, USA
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, KY 40292, USA
- Corresponding author
| | - Nazarul Hasan
- Department of Biochemistry and Molecular Genetics, University of Louisville, Louisville, KY 40292, USA
| | - Bart G. Borghuis
- Department of Anatomical Sciences and Neurobiology, University of Louisville, Louisville, KY 40292, USA
- Corresponding author
| |
Collapse
|
7
|
Iwata T. Japan to Global Eye Genetics Consortium: Extending Research Collaboration for Inherited Eye Diseases. Asia Pac J Ophthalmol (Phila) 2022; 11:360-368. [PMID: 35904986 DOI: 10.1097/apo.0000000000000535] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Accepted: 03/24/2022] [Indexed: 12/24/2022] Open
Abstract
Japan Eye Genetics Consortium (JEGC) was established in 2011 to migrate research system to all-Japan structure for collecting phenotype-genotype information for inherited retinal diseases and other retinal diseases including hereditary optic neuropathy and hereditary glaucoma. Diagnostic team was assembled to maintain quality of diagnostic and to collect phenotype information to database in Tokyo Medical Center (TMC). Over the past 10 years, 1538 pedigree [2788 deoxyribonucleic acid (DNA) samples] was collected from 38 ophthalmology departments and eye hospitals. Whole exome analysis has improved diagnostic rate from ~17% in 2011 to 53% in 2021, with 27% of known variants, 18% of novel variants in known gene, 8% of potential novel disease-causing genes, and 47% of pedigree with unknown cause. Approximately 70% of Japanese patients were affected by novel mutation or by unknown cause. In 2014, Asian Eye Genetics Consortium (AEGC) was established by researchers from Hong Kong, India, Japan, and the US, later renamed to Global Eye Genetics Consortium (GEGC) to expand the idea of collaborative research on rare genetic eye diseases in Asia, Middle East, Africa, and South America. GEGC phenotype-genotype database, GenEye, was constructed to collect and catalog genetic eye diseases at global scale. Over 200 members from 30 countries, GEGC now has 200 members from 30 continents, performing scientific programs, young investigator visiting program, and GEGC organized session at the meetings of the Asia-Pacific Academy of Ophthalmology (APAO), The Association for Research in Vision and Ophthalmology (ARVO), All India Ophthalmological Society (AIOS), World Ophthalmology Congress (WOC), and International Society for Eye Research (ISER).
Collapse
Affiliation(s)
- Takeshi Iwata
- Molecular and Cellular Biology Division, National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center, Tokyo, Japan
| |
Collapse
|
8
|
Kim J, Park D, Seo NY, Yoon TH, Kim GH, Lee SH, Seo J, Um JW, Lee KJ, Ko J. LRRTM3 regulates activity-dependent synchronization of synapse properties in topographically connected hippocampal neural circuits. Proc Natl Acad Sci U S A 2022; 119:e2110196119. [PMID: 35022233 PMCID: PMC8784129 DOI: 10.1073/pnas.2110196119] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2021] [Accepted: 12/03/2021] [Indexed: 11/18/2022] Open
Abstract
Synaptic cell-adhesion molecules (CAMs) organize the architecture and properties of neural circuits. However, whether synaptic CAMs are involved in activity-dependent remodeling of specific neural circuits is incompletely understood. Leucine-rich repeat transmembrane protein 3 (LRRTM3) is required for the excitatory synapse development of hippocampal dentate gyrus (DG) granule neurons. Here, we report that Lrrtm3-deficient mice exhibit selective reductions in excitatory synapse density and synaptic strength in projections involving the medial entorhinal cortex (MEC) and DG granule neurons, accompanied by increased neurotransmitter release and decreased excitability of granule neurons. LRRTM3 deletion significantly reduced excitatory synaptic innervation of hippocampal mossy fibers (Mf) of DG granule neurons onto thorny excrescences in hippocampal CA3 neurons. Moreover, LRRTM3 loss in DG neurons significantly decreased mossy fiber long-term potentiation (Mf-LTP). Remarkably, silencing MEC-DG circuits protected against the decrease in the excitatory synaptic inputs onto DG and CA3 neurons, excitability of DG granule neurons, and Mf-LTP in Lrrtm3-deficient mice. These results suggest that LRRTM3 may be a critical factor in activity-dependent synchronization of the topography of MEC-DG-CA3 excitatory synaptic connections. Collectively, our data propose that LRRTM3 shapes the target-specific structural and functional properties of specific hippocampal circuits.
Collapse
Affiliation(s)
- Jinhu Kim
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 42988, Korea
| | - Dongseok Park
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 42988, Korea
| | - Na-Young Seo
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 42988, Korea
- Neural Circuits Group, Korea Brain Research Institute (KBRI), Daegu 41062, Korea
| | - Taek-Han Yoon
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 42988, Korea
| | - Gyu Hyun Kim
- Neural Circuits Group, Korea Brain Research Institute (KBRI), Daegu 41062, Korea
| | - Sang-Hoon Lee
- Neural Circuits Group, Korea Brain Research Institute (KBRI), Daegu 41062, Korea
- Brain Research Core Facilities, KBRI, Daegu 41062, Korea
| | - Jinsoo Seo
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 42988, Korea
| | - Ji Won Um
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 42988, Korea
| | - Kea Joo Lee
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 42988, Korea;
- Neural Circuits Group, Korea Brain Research Institute (KBRI), Daegu 41062, Korea
| | - Jaewon Ko
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 42988, Korea;
| |
Collapse
|
9
|
Agosto MA, Adeosun AAR, Kumar N, Wensel TG. The mGluR6 ligand-binding domain, but not the C-terminal domain, is required for synaptic localization in retinal ON-bipolar cells. J Biol Chem 2021; 297:101418. [PMID: 34793838 PMCID: PMC8671642 DOI: 10.1016/j.jbc.2021.101418] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Revised: 11/03/2021] [Accepted: 11/08/2021] [Indexed: 11/26/2022] Open
Abstract
Signals from retinal photoreceptors are processed in two parallel channels-the ON channel responds to light increments, while the OFF channel responds to light decrements. The ON pathway is mediated by ON type bipolar cells (BCs), which receive glutamatergic synaptic input from photoreceptors via a G-protein-coupled receptor signaling cascade. The metabotropic glutamate receptor mGluR6 is located at the dendritic tips of all ON-BCs and is required for synaptic transmission. Thus, it is critically important for delivery of information from photoreceptors into the ON pathway. In addition to detecting glutamate, mGluR6 participates in interactions with other postsynaptic proteins, as well as trans-synaptic interactions with presynaptic ELFN proteins. Mechanisms of mGluR6 synaptic targeting and functional interaction with other synaptic proteins are unknown. Here, we show that multiple regions in the mGluR6 ligand-binding domain are necessary for both synaptic localization in BCs and ELFN1 binding in vitro. However, these regions were not required for plasma membrane localization in heterologous cells, indicating that secretory trafficking and synaptic localization are controlled by different mechanisms. In contrast, the mGluR6 C-terminus was dispensable for synaptic localization. In mGluR6 null mice, localization of the postsynaptic channel protein TRPM1 was compromised. Introducing WT mGluR6 rescued TRPM1 localization, while a C-terminal deletion mutant had significantly reduced rescue ability. We propose a model in which trans-synaptic ELFN1 binding is necessary for mGluR6 postsynaptic localization, whereas the C-terminus has a role in mediating TRPM1 trafficking. These findings reveal different sequence determinants of the multifunctional roles of mGluR6 in ON-BCs.
Collapse
Affiliation(s)
- Melina A Agosto
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas, USA.
| | - Abiodun Adefola R Adeosun
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas, USA; Pharmacology and Chemical Biology Graduate Program, Baylor College of Medicine, Houston, Texas, USA
| | - Nitin Kumar
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas, USA
| | - Theodore G Wensel
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas, USA; Pharmacology and Chemical Biology Graduate Program, Baylor College of Medicine, Houston, Texas, USA
| |
Collapse
|
10
|
Kim HY, Um JW, Ko J. Proper synaptic adhesion signaling in the control of neural circuit architecture and brain function. Prog Neurobiol 2021; 200:101983. [PMID: 33422662 DOI: 10.1016/j.pneurobio.2020.101983] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Revised: 11/23/2020] [Accepted: 12/22/2020] [Indexed: 12/17/2022]
Abstract
Trans-synaptic cell-adhesion molecules are critical for governing various stages of synapse development and specifying neural circuit properties via the formation of multifarious signaling pathways. Recent studies have pinpointed the putative roles of trans-synaptic cell-adhesion molecules in mediating various cognitive functions. Here, we review the literature on the roles of a diverse group of central synaptic organizers, including neurexins (Nrxns), leukocyte common antigen-related receptor protein tyrosine phosphatases (LAR-RPTPs), and their associated binding proteins, in regulating properties of specific type of synapses and neural circuits. In addition, we highlight the findings that aberrant synaptic adhesion signaling leads to alterations in the structures, transmission, and plasticity of specific synapses across diverse brain areas. These results seem to suggest that proper trans-synaptic signaling pathways by Nrxns, LAR-RPTPs, and their interacting network is likely to constitute central molecular complexes that form the basis for cognitive functions, and that these complexes are heterogeneously and complexly disrupted in many neuropsychiatric and neurodevelopmental disorders.
Collapse
Affiliation(s)
- Hee Young Kim
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, 42988, South Korea
| | - Ji Won Um
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, 42988, South Korea; Core Protein Resources Center, DGIST, Daegu, 42988, South Korea.
| | - Jaewon Ko
- Department of Brain and Cognitive Sciences, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu, 42988, South Korea.
| |
Collapse
|