Survival response-linked Pyk2 activation during potassium depletion-induced apoptosis of cerebellar granule neurons

Using High-Throughput Animal or Cell-Based Models to Functionally Characterize GWAS Signals

PURPOSE OF REVIEW

The advent of genome-wide association studies (GWASs) constituted a breakthrough in our understanding of the genetic architecture of multifactorial diseases. For Alzheimer's disease (AD), more than 20 risk loci have been identified. However, we are now facing three new challenges: (i) identifying the functional SNP or SNPs in each locus, (ii) identifying the causal gene(s) in each locus, and (iii) understanding these genes' contribution to pathogenesis.

RECENT FINDINGS

To address these issues and thus functionally characterize GWAS signals, a number of high-throughput strategies have been implemented in cell-based and whole-animal models. Here, we review high-throughput screening, high-content screening, and the use of the Drosophila model (primarily with reference to AD).

SUMMARY

We describe how these strategies have been successfully used to functionally characterize the genes in GWAS-defined risk loci. In the future, these strategies should help to translate GWAS data into knowledge and treatments.

Transcriptional landscapes at the intersection of neuronal apoptosis and substance P-induced survival: exploring pathways and drug targets

A change in the delicate equilibrium between apoptosis and survival regulates the neurons fate during the development of nervous system and its homeostasis in adulthood. Signaling pathways promoting or protecting from apoptosis are activated by multiple signals, including those elicited by neurotrophic factors, and depend upon specific transcriptional programs. To decipher the rescue program induced by substance P (SP) in cerebellar granule neurons, we analyzed their whole-genome expression profiles after induction of apoptosis and treatment with SP. Transcriptional pathways associated with the survival effect of SP included genes encoding for proteins that may act as pharmacological targets. Inhibition of one of these, the Myc pro-oncogene by treatment with 10058-F4, reverted in a dose-dependent manner the rescue effect of SP. In addition to elucidate the transcriptional mechanisms at the intersection of neuronal apoptosis and survival, our systems biology-based perspective paves the way towards an innovative pharmacology based on targets downstream of neurotrophic factor receptors.

OGD induced modification of FAK- and PYK2-coupled pathways in organotypic hippocampal slice cultures

Focal adhesion kinase (FAK) and proline-rich tyrosine kinase (PYK2) are two related non-receptor tyrosine kinases which are thought to play a role in transducing extracellular matrix (ECM)-derived survival signals into cells. The functions of FAK and PYK2 are linked to autophosphorylation of their specific tyrosine residues, Tyr-397 in FAK and Tyr-402 in PYK2, and then association with different signalling proteins which mediate activation of downstream targets such as ERK and JNK mitogen-activated kinase cascades. Thus, modulation of FAK as well as PYK2 autophosphorylation may affect several intracellular pathways and may participate in a variety of pathological settings. The present study provides a systematic investigation of the influence of experimental ischemia, induced by oxygen-glucose-deprivation, on the FAK- and PYK2-mediated signalling in organotypic hippocampal slice cultures. OGD induced primary down-regulation of FAK and PYK2 autophosphorylation (at Tyr 397 and Tyr 402, respectively) at 24-48 h of reoxygenation was accompanied by the diminution of phosphorylation/activation of Src and JNK. In contrast, the activity of Akt and ERK1/2 remained on the control level. It indicates that Akt kinase as well as ERK1/2 does not interfere with OGD-induced neuronal damage. The inhibition of the early step of FAK and PYK2 activation demonstrated by the decrease of tyrosine autophosphorylation may comprise an important portion of the response expressed by modulation of some coupled signal transduction pathways.

Post-ovulatory aging of oocytes disrupts kinase signaling pathways and lysosome biogenesis

Post-ovulatory aging of oocytes results in the progressive loss of fertilization and developmental competence. This degradation of oocyte quality has been the object of numerous investigations, primarily focused on individual signaling pathways which provide limited insight into the status of global signaling events. The purpose of the present investigation was to comprehensively assess broad patterns of signaling pathway activity during in vitro aging as an initial step in defining control points that can be targeted to prevent the reduction in oocyte quality during prolonged culture. An antibody microarray-based phospho-proteome analysis performed on oocytes before and after eight hours of culture revealed significant changes in the abundance or activation state of 43 proteins that function in a wide variety of protein kinase-mediated signaling pathways. Several of the most significantly affected kinases were studied by Western blot and confocal immunofluorescence to corroborate the array results. Prolonged culture resulted in global changes in the abundance and activity of protein kinases that regulate the response to calcium, stress, and cell-cycle control. Examination of intracellular structures revealed a previously unrecognized increase in the abundance of large autophogagic lysosomes, which correlates with changes in protein kinase pathways. These results provide insight into the stresses experienced by oocytes during culture and the diversity of responses that results from them. The observed increase in autophagy-related activity, together with the disruptions in calcium signaling, cell-cycle, and stress-response pathways, have the potential to negatively impact oocyte quality by interfering with the normal sequence of biochemical changes that constitute egg activation following fertilization.

Late-Onset Alzheimer's Disease Genes and the Potentially Implicated Pathways

Late-onset Alzheimer's disease (LOAD) is a devastating neurodegenerative disease with no effective treatment or cure. In addition to APOE, recent large genome-wide association studies have identified variation in over 20 loci that contribute to disease risk: CR1, BIN1, INPP5D, MEF2C, TREM2, CD2AP, HLA-DRB1/HLA-DRB5, EPHA1, NME8, ZCWPW1, CLU, PTK2B, PICALM, SORL1, CELF1, MS4A4/MS4A6E, SLC24A4/RIN3,FERMT2, CD33, ABCA7, CASS4. In addition, rare variants associated with LOAD have also been identified in APP, TREM2 and PLD3 genes. Previous research has identified inflammatory response, lipid metabolism and homeostasis, and endocytosis as the likely modes through which these gene products participate in Alzheimer's disease. Despite the clustering of these genes across a few common pathways, many of their roles in disease pathogenesis have yet to be determined. In this review, we examine both general and postulated disease functions of these genes and consider a comprehensive view of their potential roles in LOAD risk.

Mefloquine neurotoxicity is mediated by non-receptor tyrosine kinase

Among several available antimalarial drugs, mefloquine has proven to be effective against drug-resistant Plasmodium falciparum and remains the drug of choice for both therapy and chemoprophylaxis. However, mefloquine is known to cause adverse neurological and/or psychiatric symptoms, which offset its therapeutic advantage. The exact mechanisms leading to the adverse neurological effects of mefloquine are poorly defined. Alterations in neurotransmitter release and calcium homeostasis, the inhibition of cholinesterases and the interaction with adenosine A(2A) receptors have been hypothesized to play prominent roles in mediating the deleterious effects of this drug. Our recent data have established that mefloquine can also trigger oxidative damage and subsequent neurodegeneration in rat cortical primary neurons. Furthermore, we have utilized a system biology-centered approach and have constructed a pathway model of cellular responses to mefloquine, identifying non-receptor tyrosine kinase 2 (Pyk2) as a critical target in mediating mefloquine neurotoxicity. In this study, we sought to establish an experimental validation of Pyk2 using gene-silencing techniques (siRNA). We have examined whether the downregulation of Pyk2 in primary rat cortical neurons alters mefloquine neurotoxicity by evaluating cell viability, apoptosis and oxidative stress. Results from our study have confirmed that mefloquine neurotoxicity is associated with apoptotic response and oxidative injury, and we have demonstrated that mefloquine affects primary rat cortical neurons, at least in part, via Pyk2. The implication of these findings may prove beneficial in suppressing the neurological side effects of mefloquine and developing effective therapeutic modalities to offset its adverse effects.