Prostate apoptosis response-4 (Par-4) is a protein containing both a leucine zipper and a death domain that was isolated by differential screening for genes upregulated in prostate cancer cells undergoing apoptosis. Par-4 is expressed in the nervous system, where its function is unknown. In Alzheimer disease (AD), neurons may die by apoptosis, and amyloid beta-protein (A beta) may play a role in this. We report here that Par-4 expression is increased in vulnerable neurons in AD brain and is induced in cultured neurons undergoing apoptosis. Blockade of Par-4 expression or function prevented neuronal apoptosis induced by Ab and trophic factor withdrawal. Par-4 expression was enhanced, and mitochondrial dysfunction and apoptosis exacerbated, in cells expressing presenilin-1 mutations associated with early-onset inherited AD.

No abstract

Excess glutamatergic neurotransmission may contribute to excitotoxic loss of nigrostriatal neurons in Parkinson’s disease (PD). Here, we determined if increasing glutamate uptake could reduce the extent of tyrosine hydroxylase (TH) loss in PD progression. The beta-lactam antibiotic, ceftriaxone, increases the expression of glutamate transporter 1 (GLT-1), a glutamate transporter that plays a major role in glutamate clearance in central nervous system and may attenuate adverse behavioral or neurobiological function in other neurodegenerative disease models. In association with >80 % TH loss, we observed a significant decrease in glutamate uptake in the established 6-hydroxydopamine (6-OHDA) PD model. Ceftriaxone (200 mg/kg, i.p.) increased striatal glutamate uptake with ≥ 5 consecutive days of injection in nonlesioned rats and lasted out to 14 days postinjection, a time beyond that required for 6-OHDA to produce >70 % TH loss (~9 days). When ceftriaxone was given at the time of 6-OHDA, TH loss was ~57 % compared to ~85 % in temporally matched vehicle-injected controls and amphetamine-induced rotation was reduced about 2-fold. This attenuation of TH loss was associated with increased glutamate uptake, increased GLT-1 expression, and reduced Serine 19 TH phosphorylation, a calcium-dependent target specific for nigrostriatal neurons. These results reveal that glutamate uptake can be targeted in a PD model, decrease the rate of TH loss in a calcium-dependent manner, and attenuate locomotor behavior associated with 6-OHDA lesion. Given that detection of reliable PD markers will eventually be employed in susceptible populations, our results give credence to the possibility that increasing glutamate uptake may prolong the time period before locomotor impairment occurs.

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The ubiquitous m-and -calpains are thought to be localized in the cytosolic compartment, as is their endogenous inhibitor calpastatin. Previously, -calpain was found to be enriched in mitochondrial fractions isolated from rat cerebral cortex and SH-SY5Y neuroblastoma cells, but the submitochondrial localization of -calpain was not determined. In the present study, submitochondrial fractionation and digitonin permeabilization studies indicated that both calpain 1 and calpain small subunit 1, which together form -calpain, are present in the mitochondrial intermembrane space. The N terminus of calpain 1 contains an amphipathic ␣-helical domain, and is distinct from the N terminus of calpain 2. Calpain 1, but not calpain 2, was imported into mitochondria. Removal of the N-terminal 22 amino acids of calpain 1 blocked the mitochondrial calpain import, while addition of this N-terminal region to calpain 2 or green fluorescent protein enabled mitochondrial import. The N terminus of calpain 1 was not processed following mitochondrial import, but was removed by autolysis following calpain activation. Calpain small subunit 1 was not directly imported into mitochondria, but was imported in the presence of calpain 1. The presence of a mitochondrial targeting sequence in the N-terminal region of calpain 1 is consistent with the localization of -calpain to the mitochondrial intermembrane space and provides new insight into the possible functions of this cysteine protease.Calpains (EC 3.4.22.17) are a family of Ca 2ϩ -activated cysteine proteases, including both ubiquitous and tissue-specific isoforms, that cleave their substrate proteins at discrete sites to modulate activity (1-3). The best characterized, and the predominant calpains in the central nervous system, are the classical m-and -calpains. Their physiological roles have not been fully elucidated but include cell motility, cell differentiation, membrane fusion, platelet activation, and signal transduction (3). Also extensively investigated have been the pathological roles of calpains in cell death, where calpains can cleave key structural proteins and contribute to the release of death-related proteins such as apoptosis-inducing factor (AIF) 3 (4 -9). At present, it is unclear whether the -and m-calpains have distinct or overlapping functions. They are each heterodimers consisting of a unique 80-kDa large catalytic subunit (calpain 1 or 2) and a common 28-kDa small regulatory subunit (calpain small subunit 1 or 2) (2). In vitro, the substrates of m-and -calpains are similar, if not identical (10). Knock-out of the -calpain large subunit, calpain 1, results in viable mice with reduced platelet aggregation and impaired tyrosine phosphorylation in platelets, but not overt phenotype (11). Knock-out of the m-calpain large subunit, calpain 2, or of calpain small subunit 1 (CSS1) is embryonically lethal (12)(13)(14).Both m-and -calpains are considered to be cytosolic enzymes (2,3, 15,16). An association of m-and -calpains with subcellular organelles including endoplasmic ret...