We reported earlier that the levels of Ca2+-dependent metalloproteinases are increased in Alzheimer's disease (AD) specimens, relative to control specimens. Here we show that these enzymes are forms of the matrix metalloproteinase MMP-9 (EC3.4.24. 35) and are expressed in the human hippocampus. Affinity-purified antibodies to MMP-9 labeled pyramidal neurons, but not granular neurons or glial cells. MMP-9 mRNA is expressed in pyramidal neurons, as determined with digoxigenin-labeled MMP-9 riboprobes, and the presence of this mRNA is confirmed with reverse transcriptase PCR. The cellular distribution of MMP-9 is altered in AD because 76% of the total 100 kDa enzyme activity is found in the soluble fraction of control specimens, whereas only 51% is detectable in the same fraction from AD specimens. The accumulated 100 kDa enzyme from AD brain is latent and can be converted to an active form with aminophenylmercuric acetate. MMP-9 also is detected in close proximity to extracellular amyloid plaques. Because a major constituent of plaques is the 4 kDa beta-amyloid peptide, synthetic Abeta1-40 was incubated with activated MMP-9. The enzyme cleaves the peptide at several sites, predominantly at Leu34-Met35 within the membrane-spanning domain. These results establish that neurons have the capacity to synthesize MMP-9, which, on activation, may degrade extracellular substrates such as beta-amyloid. Because the latent form of MMP-9 accumulates in AD brain, it is hypothesized that the lack of enzyme activation contributes to the accumulation of insoluble beta-amyloid peptides in plaques.

No abstract

The widespread distribution of the tumor suppressor PTEN (phosphatase and tensin homolog deleted on chromosome 10) in the adult brain suggests its role in a broad range of brain functions. Here we show evidence supporting a physical interaction of PTEN with a region in the third intracellular loop (3L4F) of the serotonin 5-HT2C receptor (5-HT2cR, formerly 5-HT1c receptor) in cell cultures. PTEN limits agonist-induced phosphorylation of 5-HT2cR through its protein phosphatase activity. We showed the probable existence of PTEN:5-HT2cR complexes in putative dopaminergic neurons in the rat ventral tegmental area (VTA), a brain region in which virtually all abused drugs exert rewarding effects by activating its dopamine neurons. We synthesized the interfering peptide Tat-3L4F, which is able to disrupt PTEN coupling with 5-HT2cR. Systemic application of Tat-3L4F or the 5-HT2cR agonist Ro600175 suppressed the increased firing rate of VTA dopaminergic neurons induced by delta9-tetrahydrocannabinol (THC), the psychoactive ingredient of marijuana. Using behavioral tests, we found that Tat-3L4F or Ro600175 blocks conditioned place preference of THC or nicotine, and that Ro600175, but not Tat-3L4F, produces anxiogenic effects, penile erection, hypophagia and motor functional suppression. These results suggest a potential strategy for treating drug addiction with the Tat-3L4F peptide.

No abstract

Three neutral proteinases from human hippocampal tissue have been identified and partially characterized using substrate gel electrophoresis. The proteinases showed activity when gelatin was used as the substrate, but had no detectable activity against casein. Based on the results of inhibition studies and the calcium requirements, it was concluded that the activities were due to calcium-dependent metalloproteinases. The apparent molecular weights were 130,000 (MP-130), 100,000 (MP-100), and 70,000 (MP-70). Half-maximal activities were observed with 20 microM Ca2+ for MP-130, 40 microM Ca2+ for MP-100, and 800 microM Ca2+ for MP-70. In the presence of Ca2+, Zn2+ reestablished the activities of the three metalloproteinases at a lower concentration than did either Co2+ or Mn2+. One millimolar Al3+ inhibited 67% of the MP-70 activity, but did not affect the MP-100 and MP-130 activities. An analysis of Alzheimer-affected hippocampal and control samples showed that the specific activity (in units per milligram of sodium dodecyl sulfate-soluble protein) of MP-70 varied less than the activities of MP-100 and MP-130 between the two groups. Although p-amino-phenylmercuric acetate (p-APMA) increased the activities of MP-70 by 70% in both groups of specimens, the resulting activities from Alzheimer samples were greater than those from control samples (p less than 0.01). A wide range of MP-100 specific activity was observed in both groups, and its mean activity was higher in Alzheimer-affected samples (p less than 0.05). Treatment with p-APMA increased the activity of MP-100 only 25% in both groups of tissue samples. MP-130 activity was detected predominantly in Alzheimer-affected hippocampal specimens, and treatment with p-APMA failed to increase its activity in both the control and the Alzheimer-affected specimens. The results demonstrate an elevated level of metalloproteinase activities, capable of degrading tissue matrix components, in the hippocampus from postmortem Alzheimer patients.

Matrix metalloproteinases (MMPs) were analyzed by immunohistochemistry and zymography in amyotrophic lateral sclerosis (ALS) and control brain and spinal cord specimens. Three major bands of enzyme activity (70, 100, and 130 kDa) were consistently observed and were subsequently identified as MMP-2 (70 kDa; also known as EC 3.4.24.24 or gelatinase A) and MMP-9 (100 and 130 kDa; also known as EC 3.4.24.35 or gelatinase B). Immunohistochemical studies established the presence of MMP-2 in astrocytes and MMP-9 in pyramidal neurons in the motor cortex and motor neurons in the spinal cord of ALS patients. Although a significant decrease in MMP-2 activity was noticed in the ALS motor cortex, statistically significant increases in MMP-9 (100-kDa) activity were observed in ALS frontal and occipital cortices (BA1O and 17) and all three spinal cord regions when compared with control specimens. The highest MMP-9 (100-kDa) activities in ALS were found in the motor cortex and thoracic and lumbar cord specimens. The abnormally high amount of MMP-9 and its possible release at the synapse may destroy the structural integrity of the surrounding matrix, thereby contributing to the pathogenesis of ALS. Key Words: Matrix metalloproteinase-CNS-Amyotrophic lateral sclerosisa 1 -Antichymotrypsin -Astrocyte-Motor neuron.

We investigated the membrane topology of Bves/ Pop1A as a foundation to dissect the molecular basis and function of Bves/Pop1A trafficking during development. Bves contains two asparagine-linked glycosylation sites within the amino terminus and three putative membrane domains. Therefore, glycosylation assays were performed to determine if the amino terminus of Bves is delivered into the endoplasmic reticulum lumen and glycosylated. We establish that Bves from chick heart and transfected cells is glycosylated, implying that the amino terminus of cell surface molecules is extracellular. Three biochemically distinct approaches were utilized to determine the orientation of the carboxyl terminus of Bves. First, glycosylation of Bves at exogenous sites within the carboxyl terminus was only observed in a construct that lacked the third membrane domain, which presumably reversed the orientation of the carboxyl terminus. Second, co-expression of full-length Bves with soluble, carboxyl-terminal Bves constructs that reside in different subcellular compartments revealed that Bves-Bves interactions occur in the cytoplasm. Third, the immunoreactivity of endogenous Bves at the cell surface of epicardial cells was dramatically enhanced with detergent. These results suggest that the membrane topology of cell surface Bves/Pop1A is composed of an extracellular amino terminus, three transmembrane domains, and a cytoplasmic carboxyl terminus. We therefore hypothesize that the carboxyl terminus regulates the cellular distribution of Bves/ Pop1A during coronary vessel development.

No abstract