The E3 ubiquitin ligase MID1 catalyzes ubiquitination and cleavage of Fu.

SHH (Sonic Hedgehog)-GLI signaling plays an important role during embryogenesis and in tumorigenesis. The survival and growth of several types of cancer depend on autonomously activated SHH-GLI signaling. A protein complex containing the ubiquitin ligase MID1 and protein phosphatase 2A regulates the nuclear localization and transcriptional activity of GLI3, a transcriptional effector molecule of SHH, in cancer cell lines with autonomously activated SHH signaling. However, the exact molecular mechanisms that mediate the interaction between MID1 and GLI3 remained unknown. Here, we show that MID1 catalyzes the ubiquitination and proteasomal cleavage of the GLI3 regulator Fu. Our data suggest that Fu ubiquitination and cleavage is one of the key elements connecting the MID1-PP2A protein complex with GLI3 activity control.

Nickel-catalyzed reductive arylation of activated alkynes with aryl iodides.

The direct, regioselective, and stereoselective arylation of activated alkynes with aryl iodides using a nickel catalyst and manganese reductant is described. The reaction conditions are mild (40 °C in MeOH, no acid or base) and an intermediate organomanganese reagent is unlikely. Functional groups tolerated include halides and pseudohalides, free and protected anilines, and a benzyl alcohol. Other activated alkynes including an amide and a ketone also reacted to form arylated products in good yields.

Bis{(R)-N-[(R)-2-benz-yloxy-1-(4-tert-butyl-phen-yl)eth-yl]-2-methyl-propane-2-sulfinamide} monohydrate.

The asymmetric unit of the title compound, 2C23H33NO2S·H2O, contains one organic mol-ecule in a general position and one co-crystallized water mol-ecule on a crystallographic twofold axis. Each water mol-ecule serves as a hydrogen-bond donor to a pair of S=O acceptors on symmetry-related mol-ecules. Thus, each trio of mol-ecules forms one title formula unit. These groupings are further connected along [010] via weak non-classical C-H⋯O hydrogen bonds.

Crystal structures of (R S)-N-[(1R,2S)-2-benz-yloxy-1-(2,6-di-methyl-phen-yl)prop-yl]-2-methyl-propane-2-sulfinamide and (R S)-N-[(1S,2R)-2-benz-yloxy-1-(2,4,6-tri-methyl-phen-yl)prop-yl]-2-methyl-propane-2-sulfinamide: two related protected 1,2-amino alcohols.

The title compounds, C22H31NO2S, (1), and C23H33NO2S, (2), are related protected 1,2-amino alcohols. They differ in the substituents on the benzene ring, viz. 2,6-di-methyl-phenyl in (1) and 2,4,6-tri-methyl-phenyl in (2). The plane of the phenyl ring is inclined to that of the benzene ring by 28.52 (7)° in (1) and by 44.65 (19)° in (2). In the crystal of (1), N-H⋯O=S and C-H⋯O=S hydrogen bonds link mol-ecules, forming chains along [100], while in (2), similar hydrogen bonds link mol-ecules into chains along [010]. The absolute structures of both compounds were determined by resonance scattering.

Nickel-catalyzed reductive conjugate addition to enones via allylnickel intermediates.

An alternative method to copper-catalyzed conjugate addition followed by enolate silylation for the synthesis of ß-disubstituted silyl enol ether products (R(1)(R(2))HCCH═C(OSiR(4)(3))R(3)) is presented. This method uses haloarenes instead of nucleophilic aryl reagents. Nickel ligated to either neocuproine or bipyridine couples an α,ß-unsaturated ketone or aldehyde (R(2)HC═CHC(O)R(3)) with an organic halide (R(1)-X) in the presence of a trialkylchlorosilane reagent (Cl-SiR(4)(3)). Reactions are assembled on the benchtop and tolerate a variety of functional groups (aldehyde, ketone, nitrile, sulfone, pentafluorosulfur, and N-aryltrifluoroacetamide), electron-rich iodoarenes, and electron-poor haloarenes. Mechanistic studies have confirmed the first example of a catalytic reductive conjugate addition of organic halides that proceeds via an allylnickel intermediate. Selectivity is attributed to (1) rapid, selective reaction of LNi(0) with chlorotriethylsilane and enone in the presence of other organic electrophiles, and (2) minimization of enone dimerization by ligand steric effects.

FOXO4-dependent upregulation of superoxide dismutase-2 in response to oxidative stress is impaired in spinocerebellar ataxia type 3.

Ataxin-3 (ATXN3), the disease protein in spinocerebellar ataxia type 3 (SCA3), binds to target gene promoters and modulates transcription by interaction with transcriptional regulators. Here, we show that ATXN3 interacts with the forkhead box O (FOXO) transcription factor FOXO4 and activates the FOXO4-dependent transcription of the manganese superoxide dismutase (SOD2) gene. Upon oxidative stress, ATXN3 and FOXO4 translocate to the nucleus, concomitantly bind to the SOD2 gene promoter and increase the expression of the antioxidant enzyme SOD2. Compared with normal ATXN3, mutant ATXN3 has a reduced capability to activate the FOXO4-mediated SOD2 expression and interferes with binding of FOXO4 to the SOD2 gene promoter. These findings are consistent with a downregulation of SOD2 in pontine brain tissue and lymphoblastoid cell (LC) lines of SCA3 patients. In response to oxidative stress, LCs from SCA3 patients show a specific impairment to upregulate SOD2 expression in correlation with a significantly increased formation of reactive oxygen species and cytotoxicity. The impairment to increase the expression of SOD2 under oxidative stress conditions is associated with a significantly reduced binding of FOXO4 to the SOD2 gene promoter in SCA3-LCs. Finally and consistent with a regulatory role of ATXN3 in SOD2 expression, knockdown of endogenous ATXN3 by RNA interference represses the expression of SOD2. These findings support that ATXN3 plays an important role in regulating the FOXO4-dependent antioxidant stress response via SOD2 and suggest that a decreased antioxidative capacity and increased susceptibility towards oxidative stress contributes to neuronal cell death in SCA3.

The anti-diabetic drug metformin reduces BACE1 protein level by interfering with the MID1 complex.

Alzheimer's disease (AD), the most common form of dementia in the elderly, is characterized by two neuropathological hallmarks: senile plaques, which are composed of Aß peptides, and neurofibrillary tangles, which are composed of hyperphosphorylated TAU protein. Diabetic patients with dysregulated insulin signalling are at increased risk of developing AD. Further, several animal models of diabetes show increased Aß expression and hyperphosphorylated tau. As we have shown recently, the anti-diabetic drug metformin is capable of dephosphorylating tau at AD-relevant phospho-sites. Here, we investigated the effect of metformin on the main amyloidogenic enzyme BACE1 and, thus, on the production of Aß peptides, the second pathological hallmark of AD. We find similar results in cultures of primary neurons, a human cell line model of AD and in vivo in mice. We show that treatment with metformin decreases BACE1 protein expression by interfering with an mRNA-protein complex that contains the ubiquitin ligase MID1, thereby reducing BACE1 activity. Together with our previous findings these results indicate that metformin may target both pathological hallmarks of AD and may be of therapeutic value for treating and/or preventing AD.

Translation of HTT mRNA with expanded CAG repeats is regulated by the MID1-PP2A protein complex.

Expansion of CAG repeats is a common feature of various neurodegenerative disorders, including Huntington's disease. Here we show that expanded CAG repeats bind to a translation regulatory protein complex containing MID1, protein phosphatase 2A and 40S ribosomal S6 kinase. Binding of the MID1-protein phosphatase 2A protein complex increases with CAG repeat size and stimulates translation of the CAG repeat expansion containing messenger RNA in a MID1-, protein phosphatase 2A- and mammalian target of rapamycin-dependent manner. Our data indicate that pathological CAG repeat expansions upregulate protein translation leading to an overproduction of aberrant protein and suggest that the MID1-complex may serve as a therapeutic target for the treatment of CAG repeat expansion disorders.