Expression of fasciculation and elongation protein zeta-1 (FEZ1) in cultured rat neonatal astrocytes

The importance of fasciculation and elongation protein zeta-1 in neural circuit establishment and neurological disorders

The human brain contains an estimated 100 billion neurons that must be systematically organized into functional neural circuits for it to function properly. These circuits range from short-range local signaling networks between neighboring neurons to long-range networks formed between various brain regions. Compelling converging evidence indicates that alterations in neural circuits arising from abnormalities during early neuronal development or neurodegeneration contribute significantly to the etiology of neurological disorders. Supporting this notion, efforts to identify genetic causes of these disorders have uncovered an over-representation of genes encoding proteins involved in the processes of neuronal differentiation, maturation, synaptogenesis and synaptic function. Fasciculation and elongation protein zeta-1, a Kinesin-1 adapter, has emerged as a key central player involved in many of these processes. Fasciculation and elongation protein zeta-1-dependent transport of synaptic cargoes and mitochondria is essential for neuronal development and synapse establishment. Furthermore, it acts downstream of guidance cue pathways to regulate axo-dendritic development. Significantly, perturbing its function causes abnormalities in neuronal development and synapse formation both in the brain as well as the peripheral nervous system. Mutations and deletions of the fasciculation and elongation protein zeta-1 gene are linked to neurodevelopmental disorders. Moreover, altered phosphorylation of the protein contributes to neurodegenerative disorders. Together, these findings strongly implicate the importance of fasciculation and elongation protein zeta-1 in the establishment of neuronal circuits and its maintenance.

Engrafted primary type-2 astrocytes improve the recovery of the nigrostriatal pathway in a rat model of Parkinson's disease

Parkinson's disease (PD) is a disorder characterized by a progressive loss of the dopaminergic neurons in the substantia nigra and a depletion of the neurotransmitter dopamine in the striatum. Our published results indicate that fasciculation and elongation protein zeta-1 (FEZ1) plays a role in the astrocyte-mediated protection of dopamine neurons and regulation of the neuronal microenvironment during the progression of PD. In this study, we examined the effects of engrafted type-2 astrocytes (T2As) with high expression of FEZ1 on the improvement of the symptoms and functional reconstruction of PD rats. T2As were stereotactically transplanted into the striatum of rats with PD induced by 6-hydroxydopamine (6-OHDA). An examination of apomorphine (APO)-induced rotations was performed to evaluate dopamine neuron damage and motor functions. Remarkably, the grafted cells survived in the lesion environment for six weeks or longer after implantation. In addition, the transplantation of T2As decrease the average velocity and the duration time of the APO-induced rotations, and increase the actuation time, as measured in the rotation behavioural tests. In the substantia nigra, the transplantation of T2As reduced the PD-induced GFAP, TH and FEZ1 downregulation. The grafted cells exclusively migrated to other regions near the injection site in the striatum and differentiated into GFAP⁺ astrocytes or TH⁺ neurons. Furthermore, by detecting monoamine neurotransmitters through high-performance liquid chromatography, we found that the nigrostriatal pathway had been repaired to some extent. Taken together, these results suggest that engrafted T2As with high expression of FEZ1 improved the symptoms and functional reconstruction of PD rats, providing a theoretical basis for FEZ1 as a potential target and engraftment of T2As as a therapeutic strategy in the treatment of PD.

Fasciculation and Elongation Protein Zeta-1 Expression in Reactive Astrocytes in a Rat Model of Frontal Lobe Injury

There are reports that depression induced by frontal lobe injury (FLI) has a devastating effect on human mental health. We previously reported that fasciculation and elongation protein zeta-1 (FEZ1) was essential for astrocytic protection of dopamine neurons. Studies of glutamate-glutamine cycle in mental illness have been reported, whereas not from the perspective of astrocytes. This study was designed to investigate the roles of astrocytic FEZ1 and glutamate-glutamine cycle after FLI. A model of FLI was established by inserting a blade into the right frontal lobe of rats. Behavioral tests were used to observe the behavioral changes of FLI rats. Neuropathologic examinations, including immunohistochemistry, were conducted. Behavioral tests showed that FLI decreased exploratory activity. Western blot analysis revealed that the expression of astroglial proteins overall decreased in the initial injury stage, as well as FEZ1. Immunohistochemistry showed a shift of FEZ1 localization from neurons in sham-lesioned rats to astrocytes in FLI rats, and showed the expression profile of glutamate transporter 1 and glutamine synthetase (GS) was consistent with Western blot observation. Our results indicate that astrocytic FEZ1 and glutamate-glutamine cycle dysfunction may be involved in the pathogenesis of depression after FLI.

Fasciculation and elongation zeta proteins 1 and 2: From structural flexibility to functional diversity

Fasciculation and elongation zeta/zygin (FEZ) proteins are a family of hub proteins and share many characteristics like high connectivity in interaction networks, they are involved in several cellular processes, evolve slowly and in general have intrinsically disordered regions. In 1985, unc-76 gene was firstly described and involved in axonal growth in C. elegans, and in 1997 Bloom and Horvitz enrolled also the human homologues genes, FEZ1 and FEZ2, in this process. While nematodes possess one gene (unc-76), mammalians have one more copy (FEZ1 and FEZ2). Several animal models have been used to study FEZ family functions like: C. elegans, D. melanogaster, R. novergicus and human cells. Complementation assays were performed and demonstrated the function conservation between paralogues. Human FEZ1 protein is more studied followed by UNC-76 and FEZ2 proteins, respectively. While FEZ1 and UNC-76 shared interaction partners, FEZ2 evolved and increased the number of protein-protein interactions (PPI) with cytoplasmatic partners. FEZ proteins are implicated in intracellular transport, acting as bivalent cargo transport adaptors in kinesin-mediated movement. Especially in light of this cellular function, this family of proteins has been involved in several processes like neuronal development, neurological disorders, viral infection and autophagy. However, nuclear functions of FEZ proteins have been explored as well, due to high content of PPI with nuclear proteins, correlating FEZ1 expression to Sox2 and Hoxb4 gene regulation and retinoic acid signaling. These recent findings open new avenue to study FEZ proteins functions and its involvement in already described processes. This review intends to reunite aspects of evolution, structure, interaction partners and function of FEZ proteins and correlate them to physiological and pathological processes.

Fasciculation and elongation protein zeta-1 (FEZ1) expression in reactive astrocytes in a rat model of Parkinson's disease

AIMS

Fasciculation and elongation protein zeta-1 (FEZ1) is a critical regulator of dopaminergic neurone differentiation and dopamine release. However, to date, few studies evaluating the expression patterns of FEZ1 in Parkinson's disease (PD) have been reported. The aim of this study was to investigate the expression and cellular localization of FEZ1 in a rat model of PD and to explore the role of FEZ1 in PD pathogenesis.

METHODS

Male Sprague-Dawley rats were randomly divided into two groups: a PD group and a sham group. A model of PD was established by injecting 6-Hydroxydopamine Hydrobromide (6-OHDA) into the right medial forebrain bundle of rats. Sham-lesioned rats were infused with equivalent amounts of saline and served as controls. The expression levels of FEZ1 mRNA and protein in striatum and substantia nigra were examined by real-time polymerase chain reaction (PCR) and by Western blot analysis respectively. Immunohistochemistry was performed to identify the cellular localization of FEZ1 in sham-lesioned and PD rats.

RESULTS

Western blot and real-time PCR analyses demonstrated that FEZ1 was present in normal rat brain striatum and substantia nigra. After the 6-OHDA injection, FEZ1 expression gradually increased, peaked and then decreased. Immunohistochemical detection showed a shift of FEZ1 expression from tyrosine hydroxylase positive neurones in sham-lesioned rats to astrocytes in PD rats.

CONCLUSIONS

Our results indicate that FEZ1 plays a role in the astrocytic protection of dopamine neurones and in the regulation of the neuronal microenvironment during the progression of PD.

Four mood stabilizers commonly induce FEZ1 expression in human astrocytes

OBJECTIVES

  Mood stabilizers influence the morphology, chemotaxis, and survival of neurons, which are considered to be related to the mood-stabilizing effects of these drugs. Although previous studies suggest glial abnormalities in patients with bipolar disorder and an effect of mood stabilizers on certain genes in astrocytes, less is known about the effects of mood stabilizers in astrocytes than in neurons. The present study identifies a common underlying response to mood stabilizers in astrocytes.

METHODS

  Human astrocyte-derived cells (U-87 MG) were treated with the four most commonly used mood stabilizers (lithium, valproic acid, carbamazepine, and lamotrigine) and subjected to microarray gene expression analyses. The most prominently regulated genes were validated by qRT-PCR and western blot analysis. The intercellular localization of one of these regulated genes, fasciculation and elongation protein zeta 1 (FEZ1), was evaluated by immunofluorescence staining.

RESULTS

  The microarray data indicated that FEZ1 was the only gene commonly induced by the four mood stabilizers in human astrocyte-derived cells. An independent experiment confirmed astrocytic FEZ1 induction at both the transcript and protein levels following mood stabilizer treatments. FEZ1 localized to the cytoplasm of transformed and primary astrocytes from the human adult brain.

CONCLUSIONS

  Our data suggest that FEZ1 may play important roles in human astrocytes, and that mood stabilizers might exert their cytoprotective and mood-stabilizing effects by inducing FEZ1 expression in astrocytes.

The brain-specific factor FEZ1 is a determinant of neuronal susceptibility to HIV-1 infection

Neurons are one of the few cell types in the human body that do not support HIV type-1 (HIV-1) replication. Although the lack of key receptors is a major obstacle to infection, studies suggest that additional functions inhibit virus replication to explain the exquisite resistance of neurons to HIV-1. However, specific neuronal factors that may explain this resistance remain to be discovered. In a screen for antiviral factors using a fibroblast line chemically mutagenized and selected for resistance to retroviral infection, we recently identified induction of rat FEZ1 (fasciculation and elongation protein zeta-1), a brain-specific protein, as the cause of this resistance. When exogenously expressed in nonneuronal cell lines rat FEZ1 blocked nuclear entry of retroviral DNA. Here, we demonstrate that among human brain cells, neurons naturally express high levels of FEZ1 compared to astrocytes or microglia cells and are correspondingly less susceptible to infection with pseudotyped HIV-1 that bypasses receptor-mediated viral entry. Demonstrating that endogenous FEZ1 was functionally important in the resistance of neurons to HIV-1 infection, siRNA-mediated knockdown of endogenous FEZ1 increased the infectivity of neurons while sensitive brain cell types like microglia became more resistant upon FEZ1 overexpression. In addition, FEZ1 expression was not induced in response to IFN treatment. As such, in contrast to other widely expressed, IFN-inducible antiviral factors, FEZ1 appears to represent a unique neuron-specific determinant of cellular susceptibility to infection in a cell type that is naturally resistant to HIV-1.