Roles of GSK-3beta and PYK2 signaling pathways in synaptic plasticity

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Biology, 2010.Cataloged from PDF version of thesis.Includes bibliographical references.Activity-dependent modification of synapses, as in long term potentiation (LTP) or long term depression (LTD), is widely believed to be a crucial mechanism for learning and memory. Molecular perturbations in these processes may underlie certain neuropsychiatric conditions. This thesis examines the role of two signaling pathways, glycogen synthase kinase 3 beta (GSK- 3beta) and proline-rich tyrosine kinase 2 (PYK2), in LTD at rat hippocampal synapses. GSK-3beta, a serine/threonine kinase implicated in the pathophysiology of schizophrenia, mood disorders, and Alzheimer's disease, is known to play a critical role in LTD. Here we report that GSK-3beta phosphorylates the postsynaptic scaffold protein PSD-95, a major determinant of synaptic strength, at the Thr- 19 residue. In hippocampal neurons, this promotes the activity-dependent dispersal of synaptic PSD-95 clusters. We found that overexpression of a phospho-null mutant (Ti 9A-PSD-95), but not a phospho-mimic mutant, blocks LTD without affecting basal synaptic function relative to wild type PSD-95 overexpression. Thus PSD-95 phosphorylation by GSK-3beta is a necessary step in LTD. [This project is a collaboration with Myung Jong Kim, and I am second author of the manuscript.] PYK2 is a calcium-dependent tyrosine kinase that is activated in cerebral ischemia and seizures. PYK2 is also known to bind PSD-95 at a region implicated in LTD signaling. Here we report a novel role for PYK2 in LTD. Chemical LTD treatment induces PYK2 phosphorylation at Tyr-402, and small hairpin RNA-mediated knockdown of PYK2 blocks LTD, but not LTP. We identify both enzymatic and non-enzymatic (scaffolding) roles for PYK2 in LTD, and find that PYK2 is required to suppress activity-dependent phosphorylation of the mitogen activated protein kinase ERK. ERK activity is believed to promote glutamate receptor insertion at synapses. Overexpression of WT-PYK2 further depresses activity-dependent ERK phosphorylation, and inhibits LTP, but not LTD. Our studies support a model whereby PYK2 antagonizes ERK signaling to promote LTD, at the expense of LTP, in hippocampal neurons. [This project is a collaboration with Myung Jong Kim and Chi-Fong Wang, and I am first author of the manuscript.]by Honor Hsin.Ph.D

Towards a consensus around standards for smartphone apps and digital mental health

Mental disorders impact one in four people worldwide, yet access to care is challenging for those who suffer from them1. Mental health apps offer the potential to overcome access barriers for the nearly three billion people projected to own a smartphone by 2020. Although there are over 10,000 mental health apps commercially available, there are few resources available to help end users (patients, clinicians and health care organizations) to evaluate the quality and suitability of these products. Thus, there is an urgent need for an agreement about appropriate standards, principles and practices in research and evaluation of these tools.We represent leaders in mHealth research, industry and health care systems from around the globe, and we seek here to promote consensus on implementing these standards and principles for the evaluation of mental health apps. At a minimum, standards should include consideration of: a) data safety and privacy, b) effectiveness, c) user experience/adherence, d) data integration. Our consensus on the challenges and recommendations in each of these areas is presented below

The impact of physical environments on outpatient mental health recovery: A design-oriented qualitative study of patient perspectives.

The physical environment has been shown to affect the emotional states of patients receiving mental health treatment, yet it remains unknown whether physical space design may play a role in optimizing the delivery of mental health care. Principles of architectural design and human-centered co-design have been applied to enhance the patient experience of facility environments; however, little is known about how patients view the impact of physical spaces on their recovery. In this qualitative study, we aimed to understand patient perspectives of how physical environments contribute to mental wellbeing and personal experiences of recovery, in the context of informing future design efforts. Semi-structured telephone interviews were conducted with 13 participants receiving outpatient mental health treatment at the Kaiser Permanente San Jose Adult Psychiatry Clinic. Interviews were transcribed and themes were extracted that could inform future design concepts. The sample was comprised of nine female and three male participants, and one unidentified-gender participant, between the ages of 26-64, and across several self-reported racial/ethnic subgroups. We found four dimensions of physical environments that participants reported as impactful: 1) sensory design elements (colors, sounds, and textures), 2) engagement qualities (intensity of distracted activity such as crafting or commuting), 3) social relational aspects (privacy or connection), and 4) affective experiences evoked by being present in the space itself (feeling safe, calm, in control, self-aware, or creative was beneficial). Many of these elements were similarly noted across clinic and non-clinic environments. This study identifies key dimensions of physical environments that can serve as potential metrics of design success in supporting and facilitating mental health recovery. In the midst of the current COVID-19 pandemic, where mental health treatment has increasingly shifted outside of traditional clinics, our findings can support patients and clinicians seeking to harness potential in situ therapeutic benefits of physical environments

The impact of physical environments on outpatient mental health recovery: A design-oriented qualitative study of patient perspectives

The physical environment has been shown to affect the emotional states of patients receiving mental health treatment, yet it remains unknown whether physical space design may play a role in optimizing the delivery of mental health care. Principles of architectural design and human-centered co-design have been applied to enhance the patient experience of facility environments; however, little is known about how patients view the impact of physical spaces on their recovery. In this qualitative study, we aimed to understand patient perspectives of how physical environments contribute to mental wellbeing and personal experiences of recovery, in the context of informing future design efforts. Semi-structured telephone interviews were conducted with 13 participants receiving outpatient mental health treatment at the Kaiser Permanente San Jose Adult Psychiatry Clinic. Interviews were transcribed and themes were extracted that could inform future design concepts. The sample was comprised of nine female and three male participants, and one unidentified-gender participant, between the ages of 26–64, and across several self-reported racial/ethnic subgroups. We found four dimensions of physical environments that participants reported as impactful: 1) sensory design elements (colors, sounds, and textures), 2) engagement qualities (intensity of distracted activity such as crafting or commuting), 3) social relational aspects (privacy or connection), and 4) affective experiences evoked by being present in the space itself (feeling safe, calm, in control, self-aware, or creative was beneficial). Many of these elements were similarly noted across clinic and non-clinic environments. This study identifies key dimensions of physical environments that can serve as potential metrics of design success in supporting and facilitating mental health recovery. In the midst of the current COVID-19 pandemic, where mental health treatment has increasingly shifted outside of traditional clinics, our findings can support patients and clinicians seeking to harness potential in situ therapeutic benefits of physical environments

Proline-Rich Tyrosine Kinase 2 Regulates Hippocampal Long-Term Depression

Proline-rich tyrosine kinase 2 (PYK2), also known as cell adhesion kinase β or protein tyrosine kinase 2b, is a calcium-dependent signaling protein involved in cell migration. Phosphorylation of residue Y402 is associated with activation of PYK2 and leads to the recruitment of downstream signaling molecules. PYK2 was previously implicated in long-term potentiation (LTP); however, the role of PYK2 in long-term depression (LTD) is unknown. Here, we report that PYK2 is activated by NMDA receptor stimulation (chemical LTD) in cultured neurons. Small hairpin RNA-mediated knockdown of PYK2 blocks LTD, but not LTP, in hippocampal slice cultures. We find that the Y402 residue and, to a lesser extent, PYK2 kinase activity contribute to PYK2's role in LTD. Knockdown experiments indicate that PYK2 is required to suppress NMDA-induced extracellular signal-regulated kinase (ERK) phosphorylation. Overexpression of PYK2 depresses NMDA-induced ERK phosphorylation and inhibits LTP, but not LTD. Our data indicate that PYK2 is critical for the induction of LTD, possibly in part by antagonizing ERK signaling in hippocampal neurons. Copyright © 2010 the authors

MINK and TNIK Differentially Act on Rap2-Mediated Signal Transduction to Regulate Neuronal Structure and AMPA Receptor Function

Misshapen/NIKs (Nck-interacting kinases)-related kinase (MINK) and closely related TRAF2/Nck-interacting kinase (TNIK) are proteins that specifically bind to activated Rap2 and are thus hypothesized to relay its downstream signal transduction. Activated Rap2 has been found to stimulate dendritic pruning, reduce synaptic density and cause removal of synaptic AMPA receptors (AMPA-Rs) (Zhu et al., 2005; Fu et al., 2007). Here we report that MINK and TNIK are postsynaptically enriched proteins whose clustering within dendrites is bidirectionally regulated by the activation state of Rap2. Expression of MINK and TNIK in neurons is required for normal dendritic arborization and surface expression of AMPA receptors. Overexpression of a truncated MINK mutant unable to interact with Rap2 leads to reduced dendritic branching and this MINK-mediated effect on neuronal morphology is dependent upon Rap2 activation. While similarly truncated TNIK also reduces neuronal complexity, its effect does not require Rap2 activity. Furthermore, Rap2-mediated removal of surface AMPA-Rs from spines is entirely abrogated by coexpression of MINK, but not TNIK. Thus, although both MINK and TNIK bind GTP-bound Rap2, these kinases employ distinct mechanisms to modulate Rap2-mediated signaling. MINK appears to antagonize Rap2 signal transduction by binding to activated Rap2. We suggest that MINK interaction with Rap2 plays a critical role in maintaining the morphological integrity of dendrites and synaptic transmission.National Institutes of Health (U.S) (MH076936)Canadian Institutes of Health Researc

Phosphorylation of Threonine-19 of PSD-95 by GSK-3β is Required for PSD-95 Mobilization and Long-Term Depression

Activity of glycogen synthase kinase-3β (GSK-3β) is required for long-term depression (LTD) via molecular mechanisms that are incompletely understood. Here, we report that PSD-95, a major scaffold protein of the postsynaptic density (PSD) that promotes synaptic strength, is phosphorylated on threonine-19 (T19) by GSK-3β. In cultured rat hippocampal neurons, phosphorylation of T19 increases rapidly with chemical LTD and is attenuated by pharmacologic or genetic suppression of GSK-3β. In organotypic rat hippocampal slices, we find that a nonphosphorylatable PSD-95 mutant (T19A) tagged with photoactivatable green fluorescent protein (PAGFP) shows enhanced stability in dendritic spines versus wild-type PSD-95, whereas the phosphomimetic mutant (PSD-95-T19D) is more readily dispersed. Further, overexpression of PSD-95-T19A, but not WT-PSD-95, impairs AMPA receptor internalization and the induction of LTD. These data indicate that phosphorylation on T19 by GSK-3β destabilizes PSD-95 within the PSD and is a critical step for AMPA receptor mobilization and LTD