Silvia Zucchelli - Academia.edu (original) (raw)

Papers by Silvia Zucchelli

Human Molecular Genetics, 2010

Parkinson's disease (PD) is a neurodegenerative disorder characterized by loss of dopaminergic ne... more Parkinson's disease (PD) is a neurodegenerative disorder characterized by loss of dopaminergic neurons in the Substantia Nigra and the formation of ubiquitin-and alpha-synuclein (aSYN)-positive cytoplasmic inclusions called Lewy bodies (LBs). Although most PD cases are sporadic, families with genetic mutations have been found. Mutations in PARK7/DJ-1 have been associated with autosomal recessive early-onset PD, while missense mutations or duplications of aSYN (PARK1, PARK4) have been linked to dominant forms of the disease. In this study, we identify the E3 ubiquitin ligase tumor necrosis factor-receptor associated factor 6 (TRAF6) as a common player in genetic and sporadic cases. TRAF6 binds misfolded mutant DJ-1 and aSYN. Both proteins are substrates of TRAF6 ligase activity in vivo. Interestingly, rather than conventional K63 assembly, TRAF6 promotes atypical ubiquitin linkage formation to both PD targets that share K6-, K27and K29-mediated ubiquitination. Importantly, TRAF6 stimulates the accumulation of insoluble and polyubiquitinated mutant DJ-1 into cytoplasmic aggregates. In human post-mortem brains of PD patients, TRAF6 protein colocalizes with aSYN in LBs. These results reveal a novel role for TRAF6 and for atypical ubiquitination in PD pathogenesis.

Proceedings of The National Academy of Sciences, 2006

Ca-activated Cl channels are an important component of olfactory transduction. Odor binding to ol... more Ca-activated Cl channels are an important component of olfactory transduction. Odor binding to olfactory receptors in the cilia of olfactory sensory neurons (OSNs) leads to an increase of intraciliary Ca concentration by Ca entry through cyclic nucleotide-gated (CNG) channels. Ca activates a Cl channel that leads to an efflux of Cl from the cilia, contributing to the amplification of the OSN depolarization. The molecular identity of this Cl channel remains elusive. Recent evidence has indicated that bestrophins are able to form Ca-activated Cl channels in heterologous systems. Here we have analyzed the expression of bestrophins in the mouse olfactory epithelium and demonstrated that only mouse bestrophin-2 (mBest2) was expressed. Single-cell RT-PCR showed that mBest2 was expressed in OSNs but not in supporting cells. Immunohistochemistry revealed that mBest2 was expressed on the cilia of OSNs, the site of olfactory transduction, and colocalized with the main CNGA2 channel subunit. Electrophysiological properties of Ca-activated Cl currents from native channels in dendritic knob͞cilia of mouse OSNs were compared with those induced by the expression of mBest2 in HEK-293 cells. We found the same anion permeability sequence, small estimated single-channel conductances, a Ca sensitivity difference of one order of magnitude, and the same side-specific blockage of the two Cl channel blockers commonly used to inhibit the odorant-induced Ca-activated Cl current in OSNs, niflumic acid, and 4-acetamido-4-isothiocyanato-stilben-2,2-disulfonate (SITS). Therefore, our data suggest that mBest2 is a good candidate for being a molecular component of the olfactory Ca-activated Cl channel.

Cell Death and Differentiation, 2009

Mutations in PARK7 DJ-1 have been associated with autosomal-recessive early-onset Parkinson's dis... more Mutations in PARK7 DJ-1 have been associated with autosomal-recessive early-onset Parkinson's disease (PD). This gene encodes for an atypical peroxiredoxin-like peroxidase that may act as a regulator of transcription and a redox-dependent chaperone. Although large gene deletions have been associated with a loss-of-function phenotype, the pathogenic mechanism of several missense mutations is less clear. By performing a yeast two-hybrid screening from a human fetal brain library, we identified TRAF and TNF receptor-associated protein (TTRAP), an ubiquitin-binding domain-containing protein, as a novel DJ-1 interactor, which was able to bind the PD-associated mutations M26I and L166P more strongly than wild type. TTRAP protected neuroblastoma cells from apoptosis induced by proteasome impairment. In these conditions, endogenous TTRAP relocalized to a detergent-insoluble fraction and formed cytoplasmic aggresome-like structures. Interestingly, both DJ-1 mutants blocked the TTRAP protective activity unmasking a c-jun N-terminal kinase (JNK)-and p38-MAPK (mitogen-activated protein kinase)mediated apoptosis. These results suggest an active role of DJ-1 missense mutants in the control of cell death and position TTRAP as a new player in the arena of neurodegeneration.

Journal of Biological Chemistry, 2010

Mutations in PARK7/DJ-1 are associated with autosomal recessive, early onset Parkinson disease (P... more Mutations in PARK7/DJ-1 are associated with autosomal recessive, early onset Parkinson disease (PD). DJ-1 is an atypical peroxiredoxin-like peroxidase that may act as a redox-dependent chaperone and a regulator of transcription. Here we show that DJ-1 plays an essential role in the expression of rearranged during transfection (RET), a receptor for the glial cell line-derived neurotrophic factor, a neuroprotective molecule for dopaminergic neurons, the main target of degeneration in PD.

Journal of Biological Chemistry, 2007

Here we use computational methods and biological assays to investigate the relationship between D... more Here we use computational methods and biological assays to investigate the relationship between DJ-1 missense mutations and the protein oligomeric state. Molecular dynamics (MD) calculations suggest that: (i) the structure of DJ-1 wild-type (WT) in aqueous solution, in both oxidized and reduced forms, is similar to the crystal structure of the reduced form (3, 4); (ii) the PD-causing M26I variant is structurally similar to the WT, consistent with the experimental evidence showing the protein is a dimer as WT ((5-7) and in this work); (iii) R98Q is structurally similar to the WT, consistent with the fact that this is a physiological variant (8); (iv) the L166P monomer rapidly evolves towards a conformation significantly different than WT, suggesting a change in its ability to oligomerize (3, 4). Our combined computational and experimental approach is next used to identify a mutant (R28A) that, in contrast to L166P, destabilizes the dimer subunit-subunit interface without significantly changing secondary structure elements.