A role for integrin receptors in attenuating neuronal death

Poster Presentation:

Molecular and Cellular Biology

s47

was introduced into its most C-terminal portion, or a fusion protein in which the N-terminal soluble region is directly fused to HRIO followed by a reporter protein, was tmnalated either in vitro in the presence of ER or in cultured cells, and they were examined for glycosylation. Presence of the glycosylated species indicates that the HRIO itself has the competence to span the membrane from the cytosol to the lummal space. (ii) To elucidate the mechanism underlying the formation of the novel embedded structure of HR9, requirement of HR8 for its topogeneais was assessed by translating an HRB-deleted fusion protein in vitro and by examining the Nglycosylation onto the reporter regmn fused to the C-terminus. Our results indicate that deletion of HR8 resulted in a membrane spanning of HR9, implying an important role of HR8 in the formation of the novel embedded structure of the HR9 portion.

DEPHOSPHORYLATION ROPSYCHIATRIC

OF TAU PROTEIN

INDUCED

BY NEU-

DRUGS.

Abnormally hyperphosphorylated tau found as a major component of paired helical filaments in AlLheimer disease (AD) brain, 1s reported tu strongly inhibit microtubule assembly and is also present in the affected neurons as amorphous aggregates. Therefore inhibition of abnormal phosphorylation of tau is thought to be one of Important therapeutic strategies. Glycogen synthase kinase-3 (GSK-3) is one of proline-directed kinases. that strongly phosphorylate tau protein at the sites shown to be phosphorylated in AD brain. Furthermore, It was reported that GSK-3 was co-localized with hyperphnphorylated tau in degenerating neurons in AD brains and that the amount of GSK-3 was increased in the cytosol fraction. One of the intracellular signal transduction pathways which controls the GSK-3 activity, is the phosphatidylinositol 3.kinase (P13K) pathway. In this pathway protein kinase B (PKB) is thought to phosphorylate GSK-3 and this phosphorylation abolishes the GSK-3 kinase activity. Previously we demonstrated that the process of apoptosia including activation of caspase 3 induced activation uf protein kinase C (PKC), which led to inactivation of GSK-3 (Tsujio, I., et al., FEBS Lett. in press). Therefore both of PKB and PKC are important for the regulation of GSK-3 activity. In the present study we tried to decrease the phosphorylation levels of tau protein in the cultured cell system. Among several neuropsychiatnc drugs, lithium or valproic acid was able to induce dephosphorylation of tau protein m SYSY human neuroblastoma cells. Both drugs inhibited GSK-3 directly, and also affected the upstream of GSK-3, including both of PKB and PKC, in intracellular signal transduction system. It is suggested that either dmxt or indirect effects to Inactivate GSK3 might contribute to normalize the abnormal phosphorylatmn of tau protem in living cells and that those ways might be attenuate the neuronal degenerative proces\ in Alrheimer’s disease.

pi3J

WITHDRAWN

A ROLE

FOR

INTEGRIN

RECEPTORS

IN ATTENUATING

NEU-

RONALDEATH D. S Gory, M. P Muttson, National lnvtitute on Aging, Baltimore, MD Interactions between cells and the extracellular matrix (ECM), which occur via integrin receptors, are becoming better understood. Integrin-ECM interactions mediate several biological functions including control of vascular endothelial cell activity and regulation of neurite outgrowth in the CNS. Integrina can transduce anti-death signals in non-neuronal cells. We now document a nemoprotective function of integrins in embryonic hippocampal neurons. Neurons grown on laminin, an i&grin Ii&and, exhibit increased resistance to glutamate-induced apoptosis compared to neuron grown on polylysine. Neurona expressed integrin pl and treatment of cultures with an antibody against integrin PI abolished the protective effect of laminin. Neurons maintained on laminin exhibited a sustained activation of the Akt signaling pathway demonstrated in immunoblot and immunocytochemical analyses using an antibody that selectively recognizes phosphorylated Akt. The neuroprotective effect of integrin engagement by laminin was abolished by treatment of neurons with the PI3 kinase inhibitor wortmanin. Activation of the PI3 kinase pathway by integrin engagement resulted in increased levels of the anti-apoptotic protein Bcl-2. We conclude that integrins can provide anti-death signaling in neurons, and speculate that aberrant integrin-mediated signaling may play roles in neurodegenerative disorders.

THE

CHARACTERISTICS

VASCULAR DERLY

DEMENTIA

OF IN

ANEMIA COMMUNITY

ASSOCIATED DWELLlNG

WITH EL-

AUSTRALIANS.

Elizuheth A Milward, David A Grayson, Scott Why&, Univ of Sydney, Sydney Ausrulia; H&n Crrasey, Concord Hasp, CERA, Sydney Australia; Margaret Janu, Univ of Sydney, Sydney Australia; G Anthony Broe, Concord Reparriation Gen Hasp, Svdnq Australia Around 10-200/o of older people in developed countries like the USA, UK and Australia are anemic. After a Mayo clinic report of an association of anemia and Alzheimer’s disease (Beard et al. Am J Epidemiol 1997), we observed a specific association between anemia and vascular dementia in randomly selected, community dwelling, elderly Australians. Almost half of all subjects clinically diagnosed with vascular dementia were anemic by WHO criteria. The more anemic subJecs were over twe times likelier to have VAD than other subjects (Mdward et al. NeuroReport 1999). Anemia can exacerbate cerebral &hernia and could precipitate or amplify VAD symptoms m older people with vasculopathy. We now report characterization of the anemias in the same group of elderly people (n=268, mean age at blood collection 84.9k3.7 yr). The anemia associated with VAD was primarily normocytic, though often poikdocytic or anisocytic and with lower red cell volumes than other elderly (p=O.O14), normochromic but with lower mean cell hemoglobin than other elderly (p=O.O02) and not associated with low vitamin 812 or folate measures. Repotted use of 812 and folate supplements correlated with these measures (2.tailed p=O.OOO). Anemia associated with VAD was not readily attributable to drugs, including NSAIDa (p=O.587). or benzodiazepinea, used by disturbingly many subjects (nearly 30%. p=O.126). Beta blockers were potentially protective (piO.043). not being used by subjects with VAD (anemic or not), and need more study, but no other drugs with cardiovascular 01 gastrointestinal actions correlated with anemia (p>O.O5) (though unknown interactions remain possible). While most anemic VAD subjects were not clinically iron deficient, measures were typically low (p