Akt-dependent expression of NAIP-1 protects neurons against amyloid-{beta} toxicity

Neurotrophins are a family of growth factors that attenuate several forms of pathological neuronal cell death and may represent a putative therapeutic approach to neurodegenerative diseases. In Alzheimer disease, amyloid-beta (Abeta) is thought to play a central role in the neuronal death occurring in brains of patients. In the present study, we evaluate the ability of neurotrophin-3 (NT-3) to protect neurons against the toxicity induced by aggregated Abeta. We showed that in primary cultures of cortical neurons, NT-3 reduces Abeta-induced apoptosis by limiting caspase-8, caspase-9, and caspase-3 cleavage. This neuroprotective effect of NT-3 was concomitant to an increased level of Akt phosphorylation and was abolished by an inhibitor of the phosphatidylinositol-3 kinase (PI-3K), LY294002. In parallel, NT-3 treatment reduced Abeta induced caspase-3 processing to control levels. In an attempt to link PI-3K/Akt to caspase inhibition, we evaluated the influence of the PI-3K/Akt axis on the expression of a member of the inhibitors of apoptosis proteins (IAPs), the neuronal apoptosis inhibitory protein-1. We demonstrated that NT-3 induces an up-regulation of neuronal apoptosis inhibitory protein-1 expression in neurons that promotes the inhibition of Abeta-induced neuronal apoptosis. Together, these findings demonstrate that NT-3 signaling counters Abeta-dependent neuronal cell death and may represent an innovative therapeutic intervention to limit neuronal death in Alzheimer disease.     

Substrate-induced interconversion of protein quaternary structure isoforms

Human porphobilinogen synthase (PBGS) can exist in two dramatically different quaternary structure isoforms, which have been proposed to be in dynamic equilibrium. The quaternary structure isoforms of PBGS result from two alternative conformations of the monomer; one monomer structure assembles into a high activity octamer, whereas the other monomer structure assembles into a low activity hexamer. The kinetic behavior of these oligomers led to the hypothesis that turnover facilitates the interconversion of the oligomeric structures. The current work demonstrates that the interactions of ligands at the enzyme active site promote the structural interconversion between human PBGS quaternary structure isoforms, favoring formation of the octamer. This observation illustrates that the assembly and disassembly of oligomeric proteins can be facilitated by the protein motions that accompany enzymatic catalysis.     

The cyclin-dependent kinase inhibitor p27Kip1 is stabilized in G(0) by Mirk/dyrk1B kinase

Elevated levels of the cyclin-dependent kinase (CDK) inhibitor p27 block the cell in G(0)/G(1) until mitogenic signals activate G(1) cyclins and initiate proliferation. Post-translational regulation of p27 by different phosphorylation events is critical in allowing cells to proceed through the cell cycle. We now demonstrate that the arginine-directed kinase, Mirk/dyrk1B, is maximally active in G(0) in NIH3T3 cells, when it stabilizes p27 by phosphorylating it at Ser-10. The phospho-mimetic mutant p27-S10D was more stable, and the non-phosphorylatable mutant p27-S10A was less stable than wild-type when expressed in G(0)-arrested cells. Following phosphorylation by Mirk, p27 remains a functional CDK inhibitor, capable of binding to CDK2. Mirk did not induce the translocation of p27 from the nucleus in G(0), but instead co-localized with nuclear p27. Depletion of Mirk by RNA interference decreased the phosphorylation of p27 at Ser-10 and the stability of endogenous p27. RNA(i) to Mirk increased cell entry from G(0) into G(1) as shown by increased expression of proliferating cell nuclear antigen and decreased expression of p27. These data suggest a model in which Mirk increases the amount of nuclear p27 by stabilizing it during G(0) when Mirk is most abundant. Mitogen stimulation then causes cells to enter G(1), reduces Mirk levels (Deng, X., Ewton, D., Pawlikowski, B., Maimone, M., and Friedman, E. (2003) J. Biol. Chem. 278, 41347-41354), and initiates the translocation of p27 to the cytoplasm. In addition, depletion of Mirk by RNA(i) in postmitotic C2C12 myoblasts decreased protein but not mRNA levels of p27, suggesting that stabilization of p27 by Mirk also occurs during differentiation.     

Glycogen synthase kinase-3beta regulates growth, calcium homeostasis, and diastolic function in the heart

Glycogen synthase kinase (GSK) 3beta is a negative regulator of stress-induced cardiomyocyte hypertrophy. It is not clear, however, if GSK-3beta plays any role in regulating normal cardiac growth and cardiac function. Herein we report that a transgenic mouse expressing wild type GSK-3beta in the heart has a dramatic impairment of normal post-natal cardiomyocyte growth as well as markedly abnormal cardiac contractile function. The most striking phenotype, however, is grossly impaired diastolic relaxation, which leads to increased filling pressures of the left ventricle and massive atrial enlargement. This is due to profoundly abnormal calcium handling, leading to an inability to normalize cytosolic [Ca2+] in diastole. The alterations in calcium handling are due at least in part to direct down-regulation of the sarcoplasmic reticulum calcium ATPase (SERCA2a) by GSK-3beta, acting at the level of the SERCA2 promoter. These studies identify GSK-3beta as a regulator of normal growth of the heart and are the first of which we are aware, to demonstrate regulation of expression of SERCA2a, a critical determinant of diastolic function, by a cytosolic signaling pathway, the activity of which is dynamically modulated. De-regulation of GSK-3beta leads to severe systolic and diastolic dysfunction and progressive heart failure. Because down-regulation of SERCA2a plays a central role in the diastolic and systolic dysfunction of patients with heart failure, these findings have potential implications for the therapy of this disorder.     

Multiple sampling for increasing the diagnostic sensitivity of nipple aspirate fluid for atypical cytology

OBJECTIVE: To determine if repeated collection of nipple aspirate fluid (NAF) can improve the diagnostic sensitivity for cytologic atypia, a marker of increased risk of breast cancer. STUDY DESIGN: Two hundred sixty-seven women without known breast disease volunteered for NAF cytology at 5 6-month intervals over 2 years. NAF samples were prepared on Millipore filters (Millipore Filter Corp., Bedford, Massachusetts, U.S.A.) and stained with a modified Papanicolaou method. Fluid availability and cellular abnormalities were evaluated for each collection attempt. Cellular findings were classified as benign, hyperplasia or atypia. RESULTS: NAF was obtained from 178 women (66.6%) at the first visit and from an additional 15, 10, 2 and 4 women at visits 2, 3, 4 and 5, respectively, for a cumulative total of 78.2% by visit 5. The number of women yielding NAF containing hyperplastic or atypical epithelial cells was determined at each visit. Hyperplastic cells were found in 34 (19.1%) at visit 1 and in an additional 20, 10, 5 and 4 women at visits 2, 3, 4 and 5, respectively. Atypical epithelial cells were present in 12 (6.7%) women at the initial visit and in an additional 11, 7, 5 and 1 women at visits 2, 3, 4 and 5, respectively, for a cumulative percent of 18.2 at visit 5. NAF could not be obtained from 58 women at any visit. CONCLUSION: These findings suggest that an optimum collection method for NAF cytology should consist of at least 3 or 4 separate fluid aspiration attempts. Reviewing repeated multiple samples instead of 1 increases the number of women who can be evaluated and the likelihood of detecting cytologic atypia.     

Cyclic strain-induced endothelial MMP-2: role in vascular smooth muscle cell migration

Matrix metalloproteinases (MMPs) play a vital role in vasculature response to hemodynamic stimuli via the degradation of extracellular matrix substrates. In this study, we investigated the putative role of cyclic strain-induced endothelial MMP-2 (and MMP-9) expression and release in modulating bovine aortic smooth muscle cell (BASMC) migration in vitro. Equibiaxial cyclic strain of bovine aortic endothelial cells (BAECs) leads to elevation in cellular MMP-2 (and MMP-9) expression, activity, and secretion into conditioned media, events which were time- and force-dependent. Subsequent incubation of BASMCs with conditioned media from chronically strained BAECs (5%, 24 h) significantly reduces BASMC migration (38+/-6%), an inhibitory effect which could be completely reversed by targeted siRNA 'knock-down' of MMP-2 (but not MMP-9) expression and activity in BAECs. Moreover, inhibition of strain-mediated MMP-2 expression in BAECs by protein tyrosine kinase (PTK) blockade with genistein (50 microM) was also found to completely reverse this inhibitory effect on BASMC migration. Finally, direct supplementation of recombinant MMP-2 into the BASMC migration assay was found to have no significant effect on migration. However, the effect on BASMC migration of MMP-2 siRNA transfection in BAECs could be reversed by supplementation of recombinant MMP-2 into BAEC media prior to (and for the duration of) strain. These findings reveal a potentially novel role for strain-induced endothelial MMP-2 in regulating vascular SMC migration.     

Penicillium thiersii, Penicillium angulare and Penicillium decaturense, new species isolated from wood-decay fungi in North America and their phylogenetic placement from multilocus DNA sequence analysis

We describe three new fungicolous species on the basis of phenotypic and phylogenetic differences from known species. Penicillium thiersii, P. angulare and Penicillium decaturense are described. Penicillium thiersii phenotypically is identified on the basis of several characteristics including growth rates, vesicle size and condium shape and roughening. Penicillium angulare is related most closely to P. adametzioides but differs from it by restricted growth rates and conidiophores greater than 60 μm in length. Penicillium decaturense is related most closely to P. miczynskii but differs from that species by growth rate, minimum growth temperature and pigment production on MEA. Multilocus phylogenetic analysis confirmed the genetic distinctiveness of P. decaturense and the closely related species P. miczynskii, P. chrzaszczii and P. manginii. Penicillium rivolii is a synonym of P. waksmanii on the basis of this analysis. Analysis of the EF-1α gene shows rapid changes of position, number and length of introns between the species, suggesting a recent evolutionary origin for the introns.