Browsing by Author "Edler, Michael C."

Now showing 1 - 8 of 8
  • Thumbnail Image
    Item
    The association of spinophilin with disks large-associated protein 3 (SAPAP3) is regulated by metabotropic glutamate receptor (mGluR) 5
    (Elsevier, 2018) Morris, Cameron W.; Watkins, Darryl S.; Salek, Asma B.; Edler, Michael C.; Baucum, Anthony J., II; Biology, School of Science
    Spinophilin is the most abundant protein phosphatase 1 targeting protein in the postsynaptic density of dendritic spines. Spinophilin associates with myriad synaptic proteins to regulate normal synaptic communication; however, the full complement of spinophilin interacting proteins and mechanisms regulating spinophilin interactions are unclear. Here we validate an association between spinophilin and the scaffolding protein, disks large-associated protein 3 (SAP90/PSD-95 associated protein 3; SAPAP3). Loss of SAPAP3 leads to obsessive-compulsive disorder (OCD)-like behaviors due to alterations in metabotropic glutamate receptor (mGluR) signaling. Here we report that spinophilin associates with SAPAP3 in the brain and in a heterologous cell system. Moreover, we have found that expression or activation of group I mGluRs along with activation of the mGluR-dependent kinase, protein kinase C β, enhances this interaction. Functionally, global loss of spinophilin attenuates amphetamine-induced hyperlocomotion, a striatal behavior associated with dopamine dysregulation and OCD. Together, these data delineate a novel link between mGluR signaling, spinophilin, and SAPAP3 in striatal pathophysiology.
  • Thumbnail Image
    Item
    Astrocytes Regulate the Development and Maturation of Retinal Ganglion Cells Derived from Human Pluripotent Stem Cells
    (Elsevier, 2019-02-12) VanderWall, Kirstin B.; Vij, Ridhima; Ohlemacher, Sarah K.; Sridhar, Akshayalakshmi; Fligor, Clarisse M.; Feder, Elyse M.; Edler, Michael C.; Baucum, Anthony J.; Cummins, Theodore R.; Meyer, Jason S.; Biology, School of Science
    Retinal ganglion cells (RGCs) form the connection between the eye and the brain, with this connectivity disrupted in numerous blinding disorders. Previous studies have demonstrated the ability to derive RGCs from human pluripotent stem cells (hPSCs); however, these cells exhibited some characteristics that indicated a limited state of maturation. Among the many factors known to influence RGC development in the retina, astrocytes are known to play a significant role in their functional maturation. Thus, efforts of the current study examined the functional maturation of hPSC-derived RGCs, including the ability of astrocytes to modulate this developmental timeline. Morphological and functional properties of RGCs were found to increase over time, with astrocytes significantly accelerating the functional maturation of hPSC-derived RGCs. The results of this study clearly demonstrate the functional and morphological maturation of RGCs in vitro, including the effects of astrocytes on the maturation of hPSC-derived RGCs.
  • Thumbnail Image
    Item
    Mechanisms and Consequences of Dopamine Depletion-Induced Attenuation of the Spinophilin/Neurofilament Medium Interaction
    (Hindawi, 2017) Hiday, Andrew C.; Edler, Michael C.; Salek, Asma B.; Morris, Cameron W.; Thang, Morrent; Rentz, Tyler J.; Rose, Kristie L.; Jones, Lisa M.; Baucum, Anthony J., II; Biology, School of Science
    Signaling changes that occur in the striatum following the loss of dopamine neurons in the Parkinson disease (PD) are poorly understood. While increases in the activity of kinases and decreases in the activity of phosphatases have been observed, the specific consequences of these changes are less well understood. Phosphatases, such as protein phosphatase 1 (PP1), are highly promiscuous and obtain substrate selectivity via targeting proteins. Spinophilin is the major PP1-targeting protein enriched in the postsynaptic density of striatal dendritic spines. Spinophilin association with PP1 is increased concurrent with decreases in PP1 activity in an animal model of PD. Using proteomic-based approaches, we observed dopamine depletion-induced decreases in spinophilin binding to multiple protein classes in the striatum. Specifically, there was a decrease in the association of spinophilin with neurofilament medium (NF-M) in dopamine-depleted striatum. Using a heterologous cell line, we determined that spinophilin binding to NF-M required overexpression of the catalytic subunit of protein kinase A and was decreased by cyclin-dependent protein kinase 5. Functionally, we demonstrate that spinophilin can decrease NF-M phosphorylation. Our data determine mechanisms that regulate, and putative consequences of, pathological changes in the association of spinophilin with NF-M that are observed in animal models of PD.
  • Thumbnail Image
    Item
    Mechanisms Regulating the Association of Protein Phosphatase 1 with Spinophilin and Neurabin
    (American Chemical Society, 2018-11-21) Edler, Michael C.; Salek, Asma B.; Watkins, Darryl S.; Kaur, Harjot; Morris, Cameron W.; Yamamoto, Bryan K.; Baucum, Anthony J., II; Biology, School of Science
    Protein phosphorylation is a key mediator of signal transduction, allowing for dynamic regulation of substrate activity. Whereas protein kinases obtain substrate specificity by targeting specific amino acid sequences, serine/threonine phosphatase catalytic subunits are much more promiscuous in their ability to dephosphorylate substrates. To obtain substrate specificity, serine/threonine phosphatases utilize targeting proteins to regulate phosphatase subcellular localization and catalytic activity. Spinophilin and its homologue neurabin are two of the most abundant dendritic spine-localized protein phosphatase 1 (PP1) targeting proteins. The association between spinophilin and PP1 is increased in the striatum of animal models of Parkinson's disease (PD). However, mechanisms that regulate the association of spinophilin and neurabin with PP1 are unclear. Here, we report that the association between spinophilin and PP1α or PP1γ1 was increased by CDK5 expression and activation in a heterologous cell system. This increased association is at least partially due to phosphorylation of PP1. Conversely, CDK5 expression and activation decreased the association of PP1 with neurabin. As with dopamine depletion, methamphetamine (METH) abuse causes persistent alterations in dopamine signaling which influence striatal medium spiny neuron function and biochemistry. Moreover, both METH toxicity and dopamine depletion are associated with deficits in motor control and motor learning. Pathologically, we observed a decreased association of spinophilin with PP1 in rat striatum evaluated one month following a binge METH paradigm. Behaviorally, we found that loss of spinophilin recapitulates rotarod pathology previously observed in dopamine-depleted and METH-treated animals. Together, these data have implications in multiple disease states associated with altered dopamine signaling such as PD and psychostimulant drug abuse and delineate a novel mechanism by which PP1 interactions with spinophilin and neurabin may be differentially regulated.
  • Thumbnail Image
    Item
    NCRAD iPSCs: a vital resource for the Alzheimer’s disease research community
    (Wiley, 2025-01-03) Nudelman, Kelly N.; Jackson, Trever; Marshall, Jeanine D.; Faber, Kelley M.; Ohlemacher, Sarah K.; Edler, Michael C.; Foroud, Tatiana M.; Meyer, Jason S.; Medical and Molecular Genetics, School of Medicine
    Background: The National Centralized Repository for Alzheimer’s Disease and Related Dementias (NCRAD) is continuing to develop a bank of induced pluripotent stem cells (iPSCs) that are available by request to the Alzheimer’s disease (AD) research community. Methods: As part of the pipeline for quality control of received cell lines, DNA was extracted for all lines and was submitted for whole genome sequencing (WGS). Paired‐end WGS data was generated using the Illumina NovaSeq 6000 and processed following GATK best practices using the Sentieon pipeline. WGS data was annotated with Annovar, and data was reviewed for reported cell line variants and checked with Varsome and Franklin. Sequencing data was reviewed for all nonsynonymous and splicing variants in the APP, PSEN1, PSEN2, GRN, and MAPT genes. Additionally, DNA from cell lines was genotyped in‐house by NCRAD to generate apolipoprotein E (APOE) genotypes, and this data was compared with the WGS to confirm sample identity. Basic clinical and demographic data was also collected, including sex, case/control status, age, race, and ethnicity. Results: To date, DNA has been extracted and genotyped at NCRAD for lines from 183 participants including generation of APOE genotypes passing quality control. Of these, 120 cell lines have returned WGS data passing quality control. Table 1 describes the demographic and clinical features for these lines, which include data for lines from 90 individuals as well as data for 30 isogenic lines. Of the 120 lines with available WGS, there are 13 case APP variant carriers, 13 case MAPT variant carriers, 8 case PSEN1 variant carriers, and 2 case PSEN2 variant carriers. Additionally, these cell lines included two control carriers of variants of uncertain significance (VUS) in GRN or PSEN2, as well as two cases carrying VUS in PSEN1 or APP. Conclusions: NCRAD continues to expand iPSCs for the research community; adding WGS data to this resource provides an expanded scope for pre‐screening as well as functional research. Future directions include review of variants being tested in the Model Organism Development & Evaluation for Late‐Onset AD (MODEL‐AD) to provide additional value to researchers.
  • Thumbnail Image
    Item
    Neurodegeneration Focused Biorepositories: NCRAD, BioSEND, MJFF
    (Wiley, 2025-01-09) Edler, Michael C.; Lacy, Kaci; Snoddy, Casey; Mitchell, Colleen M.; Case, K. Rose; Hobbick, Chris; Nudelman, Kelly N.; Hamer, Jan; Wegel, Claire; Faber, Kelley M.; Jackson, Jacqueline M.; Foroud, Tatiana M.; Medical and Molecular Genetics, School of Medicine
    Background: Biorepositories play an integral role in the advancement of our understanding of neurodegenerative diseases and improving human health outcomes. Research efforts are accelerated when access to high‐quality clinical specimens is made available from a large, diverse participant group. Indiana University is home to three important neurodegenerative disease‐focused biorepositories including the NIA‐funded National Centralized Repository for Alzheimer’s Disease and Related Dementias (NCRAD), the NINDS‐funded Biospecimen Exchange for Neurological Disorders (BioSEND), and the Michael J. Fox Foundation (MJFF) biorepository. Having all three repositories in one location presents a unique opportunity to leverage common protocols and shared resources to provide researchers with access to a wide breadth of specimens, facilitating broad specimen sharing and standardization across studies and repositories. Method: All three repositories provide exceptional data and study coordination, data management, scientific support, and technical resources. Uniform best practice standard operating procedures (SOPs) and materials for collection and processing of samples yield consistently high‐quality specimens across studies from all repositories. Banked specimen types include DNA, RNA, whole blood, plasma, serum, cerebrospinal fluid, urine, stool, brain tissue, peripheral blood mononuclear cells (PBMCs), fibroblasts, and induced pluripotent stem cells (iPSCs). Online catalogs are available for specimen selection along with project management that can assist in the selection and approval of specimens across studies and repositories. Result: Among the three repositories, over 4 million specimen aliquots from more than 150 studies have been banked. This collection represents over 142,000 unique participants across a diverse array of neurodegenerative diseases, including Alzheimer’s disease, Parkinson’s disease, Amyotrophic Lateral Sclerosis, Frontotemporal Dementia, Lewy Body Dementia, Concussion, Traumatic Brain Injury, Huntington’s Disease, Spinocerebellar Ataxia and other neurodegenerative proteinopathies. More than 600,000 specimen aliquots have been distributed to over 370 investigators, resulting in almost 1,000 publications. Conclusion: NCRAD, BioSEND, and MJFF serve as crucial resources for investigators requiring high‐quality clinical specimens collected and processed in accordance with best practice SOPs. The centralized location at Indiana University provides the opportunity to synergize and align common study objectives to provide shared resources with broader sample diversity, increased statistical power, improved reproducibility, and enhanced opportunities for broad specimen sharing, thereby fostering collaborative research initiatives.
  • Thumbnail Image
    Item
    Spinophilin regulates phosphorylation and interactions of the GluN2B subunit of the N-methyl-d-aspartate receptor
    (Wiley, 2019-08-02) Salek, Asma B.; Edler, Michael C.; McBride, Jonathon P.; Baucum, Anthony J.; Pharmacology and Toxicology, School of Medicine
    N-methyl-D-Aspartate receptors (NMDARs) are abundant postsynaptic proteins that are critical for normal synaptic communication. NMDAR channel function is regulated by multiple properties, including phosphorylation. Inhibition of protein phosphatase 1 in hippocampal neurons increases NMDAR activity, an effect abrogated by loss of spinophilin, the major protein phosphatase 1 (PP1)-targeting protein in the postsynaptic density (PSD). However, how spinophilin regulates PP1-dependent NMDAR function is unclear. We hypothesize that spinophilin regulates PP1 binding to the NMDAR to alter NMDAR phosphorylation. Our data demonstrate that spinophilin interacts with the GluN2B subunit of the NMDAR. In HEK293 cells, activation and/or overexpression of protein kinase A increased the association between spinophilin and the GluN2B subunit of the NMDAR. Functionally, we found that spinophilin overexpression decreased PP1 binding to the GluN2B subunit of the NMDAR and attenuated the PP1-dependent dephosphorylation of GluN2B at Ser-1284. Moreover, in P28 hippocampal lysates isolated from spinophilin KO compared to WT mice, there was increased binding of GluN2B to PP1, decreased phosphorylation of GluN2B at Ser-1284, and altered GluN2B protein interactions with PSD-enriched proteins. Together, our data demonstrate that spinophilin decreases PP1 binding to GluN2B and concomitantly enhances the phosphorylation of GluN2B at Ser-1284. The putative consequences of these spinophilin-dependent alterations in GluN2B phosphorylation and interactions on synaptic GluN2B localization and function are discussed.
  • Thumbnail Image
    Item
    Three-Dimensional Retinal Organoids Facilitate the Investigation of Retinal Ganglion Cell Development, Organization and Neurite Outgrowth from Human Pluripotent Stem Cells
    (Springer Nature, 2018-09-28) Fligor, Clarisse M.; Langer, Kirstin B.; Sridhar, Akshayalakshmi; Ren, Yuan; Shields, Priya K.; Edler, Michael C.; Ohlemacher, Sarah K.; Sluch, Valentin M.; Zack, Donald J.; Zhang, Chi; Suter, Daniel M.; Meyer, Jason S.; Biology, School of Science
    Retinal organoids are three-dimensional structures derived from human pluripotent stem cells (hPSCs) which recapitulate the spatial and temporal differentiation of the retina, serving as effective in vitro models of retinal development. However, a lack of emphasis has been placed upon the development and organization of retinal ganglion cells (RGCs) within retinal organoids. Thus, initial efforts were made to characterize RGC differentiation throughout early stages of organoid development, with a clearly defined RGC layer developing in a temporally-appropriate manner expressing a complement of RGC-associated markers. Beyond studies of RGC development, retinal organoids may also prove useful for cellular replacement in which extensive axonal outgrowth is necessary to reach post-synaptic targets. Organoid-derived RGCs could help to elucidate factors promoting axonal outgrowth, thereby identifying approaches to circumvent a formidable obstacle to RGC replacement. As such, additional efforts demonstrated significant enhancement of neurite outgrowth through modulation of both substrate composition and growth factor signaling. Additionally, organoid-derived RGCs exhibited diverse phenotypes, extending elaborate growth cones and expressing numerous guidance receptors. Collectively, these results establish retinal organoids as a valuable tool for studies of RGC development, and demonstrate the utility of organoid-derived RGCs as an effective platform to study factors influencing neurite outgrowth from organoid-derived RGCs.