The role of STEP in Alzheimer's disease

Child Study Center, Yale University School of Medicine, New Haven, CT, USA.
Channels (Austin, Tex.) (Impact Factor: 2.32). 09/2010; 4(5):347-50. DOI: 10.4161/chan.4.5.12910
Source: PubMed

ABSTRACT Amyloid beta (Aβ), the putative causative agent in Alzheimer's disease, is known to affect glutamate receptor trafficking. Previous studies have shown that Aβ downregulates the surface expression of N-methyl D-aspartate type glutamate receptors (NMDARs) by the activation of STriatal-Enriched protein tyrosine Phosphatase 61 (STEP₆₁). More recent findings confirm that STEP₆₁ plays an important role in Aβ-induced NMDAR endocytosis. STEP levels are elevated in human AD prefrontal cortex and in the cortex of several AD mouse models. The increase in STEP₆₁ levels and activity contribute to the removal of GluN1/GluN2B receptor complexes from the neuronal surface membranes. The elevation of STEP₆₁ is due to disruption in the normal degradation of STEP₆₁ by the ubiquitin proteasome system. Here, we briefly discuss additional studies in support of our hypothesis that STEP₆₁ contributes to aspects of the pathophysiology in Alzheimer's disease. Exogenous application of Aβ-enriched conditioned medium (7PA2-CM) to wild-type cortical cultures results in a loss of GluN1/GluN2B subunits from neuronal membranes. Abeta-mediated NMDAR internalization does not occur in STEP knock-out cultures, but is rescued by the addition of active TAT-STEP to the cultures prior to Aβ treatment.

1 Follower
  • [Show abstract] [Hide abstract]
    ABSTRACT: Striatal-enriched protein tyrosine phosphatase (STEP) is a brain-specific tyrosine phosphatase that has been shown to de-phosphorylate several key neuronal signaling proteins, including kinases (ERK1/2, FYN, PYK2) and glutamate receptor subunits (NR2B, GLUR2). Step knock-out mice have increased phosphorylation of these substrates in the brain, with potential functional consequences in synaptic plasticity and cognitive tasks. It is therefore of interest to identify the molecular pathways and downstream transcriptional targets that are impacted by Step knockdown. In the present study, striatal RNA samples from Step wild-type, knock-out and heterozygous mice were hybridized to Affymetrix microarray chips and evaluated for transcriptional changes between genotypes. Pathway analysis highlighted extracellular signal-regulated kinases (Erk) signaling and multiple pathways related to neurotrophin signaling, neuronal development and synaptic transmission. Potential genes of interest identified by microarray were confirmed by quantitative real-time polymerase chain reaction (qRT-PCR) in cortex and hippocampus, which shared several transcriptional alterations with striatum. In order to evaluate Step knockdown in an in vitro system, a panel of genes were evaluated using qRT-PCR in rat cortical neurons that were transduced with lentivirus expressing short hairpin RNA against Step or a non-targeting control. Our data suggest that Step has a role in the expression of immediate early genes relevant to synaptic plasticity, in both in vitro and in vivo systems.
    Neuroscience 08/2014; 278. DOI:10.1016/j.neuroscience.2014.08.002 · 3.33 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Striatal-enriched tyrosine phosphatase (STEP) has been described as a regulator of multiple kinases and glutamate receptor subunits critical for synaptic plasticity. Published behavioral and biochemical characterization from the founder line of STEP knockout (KO) mice revealed superior cognitive performance, with enhanced phosphorylation of substrates such as ERK, Fyn and GluN2B; suggesting that inhibitors of STEP may have potential as therapeutic agents for the treatment of neuropsychiatric disorders (reviewed in Goebel-Goody et al 2012). The objectives of the present work aimed to replicate and extend the previously reported behavioral consequences of STEP knockout. Consistent with previous reported data, STEP KO mice demonstrated exploratory activity levels and similar motor coordination relative to WT littermate controls as well as intact memory in a y-maze spatial novelty test. Interestingly, KO mice demonstrated deficits in pre-pulse inhibition as well as reduced seizure threshold relative to WT controls. Immunohistochemical staining of brains revealed the expected gene-dependent reduction in STEP protein confirming knockout in the mice. The present data confirm expression and localization of STEP and the absence in KO mice, and describe functional downstream implications of reducing STEP levels in vivo.
    Genes Brain and Behavior 08/2014; 13(7). DOI:10.1111/gbb.12169 · 3.51 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Protein tyrosine phosphorylation is a key regulatory process in virtually all aspects of cellular functions. Dysregulation of protein tyrosine phosphorylation is a major cause of human diseases, such as cancers, diabetes, autoimmune disorders, and neurological diseases. Indeed, protein tyrosine phosphorylation-mediated signaling events offer ample therapeutic targets, and drug discovery efforts to date have brought over two dozen kinase inhibitors to the clinic. Accordingly, protein tyrosine phosphatases (PTPs) are considered next-generation drug targets. For instance, PTP1B is a well-known targets of type 2 diabetes and obesity, and recent studies indicate that it is also a promising target for breast cancer. SHP2 is a bona-fide oncoprotein, mutations of which cause juvenile myelomonocytic leukemia, acute myeloid leukemia, and solid tumors. In addition, LYP is strongly associated with type 1 diabetes and many other autoimmune diseases. This review summarizes recent findings on several highly recognized PTP family drug targets, including PTP1B, Src homology phosphotyrosyl phosphatase 2,(SHP2), lymphoid-specific tyrosine phosphatase (LYP), CD45, Fas associated phosphatase-1 (FAP-1), striatal enriched tyrosine phosphatases (STEP), mitogen-activated protein kinase/dual-specificity phosphatase 1 (MKP-1), phosphatases of regenerating liver-1 (PRL), low molecular weight PTPs (LMWPTP), and CDC25. Given that there are over 100 family members, we hope this review will serve as a road map for innovative drug discovery targeting PTPs.
    Acta Pharmacologica Sinica 09/2014; DOI:10.1038/aps.2014.80 · 2.50 Impact Factor