Physiological and pathological interrelationships of amyloid beta peptide and the amyloid precursor protein

Amino-Truncated β-Amyloid42 Peptides in Cerebrospinal Fluid and Prediction of Progression of Mild Cognitive Impairment

Background: Early identification of patients with mild cognitive impairment (MCI) progressing to Alzheimer disease (MCI-AD) by use of biomarkers in cerebrospinal fluid (CSF) is an essential step toward improving clinical diagnosis and drug development. We evaluated whether different β-amyloid42 (Aβ42) peptides can add further information to the combined use of tau and Aβ1–42 for predicting risk of progression of MCI to AD.

Methods: We used xMAP® technology to simultaneously quantify different Aβ42 peptides modified at the amino terminus, tau, and phosphorylated tau (P-tau181P) in CSF. Aβ42 peptide concentrations were measured by use of immunoreactivity toward Aβ monoclonal antibodies [3D6 (Aβ42-3D6), WO2 (Aβ42-WO2), 6E10 (Aβ42-6E10), and 4G8 (Aβ42-4G8)]. The discriminant ability of the markers was evaluated by ROC curve analysis.

Results: The areas under the curves for the separation of MCI-AD from nonprogressing MCI (MCI-N) were significantly higher when we used Aβ42-3D6/Aβ42-WO2, Aβ42-3D6/Aβ42-6E10, or Aβ42-3D6/Aβ42-4G8 compared with Aβ42-3D6. In addition, differentiation of MCI-N from MCI-AD was improved by quantification of full-length Aβ1–42 (Aβ42-3D6) compared with Aβ42-WO2, Aβ42-6E10, or Aβ42-4G8. Several Aβ42 peptides truncated at the amino terminus (Aβ11–42 and Aβ8–42) were identified in CSF by surface-enhanced laser desorption/ionization time-of-flight technology.

Conclusion: The CSF markers tau, Aβ42 forms, and P-tau181P, when used as adjuncts to clinical diagnosis, have the potential to help identify AD pathology and could be a valuable asset for early AD diagnosis.

Latent-TGF-beta: an overview

The latency associated with the transforming growth factor-betas (TGF-betas) was discovered in 1984. Since the two publications on this subject in that year, there has been on average over sixty reports in which latency was the dominant theme for each of the past 10 years, proof enough of the interest in this field of growth factor research. As the mature 25 kD forms of the TGF-betas are required for them to exert their many, diverse biological effects, it was inevitable that an explanation of the structure and of the activation of the latent complexes be sought. This overview provides a description of these essential points. Now that it has been clearly shown that dysregulation of particular components of the TGF-beta signalling pathway is implicated in many human diseases, the activation of the latent TGF-beta complexes has taken on added importance. Technical improvements enable the distinction of active and latent TGF-beta proteins in vivo and have started to reveal anomalies in the control of activation in relation to various pathological situations.

X11 interaction with beta-amyloid precursor protein modulates its cellular stabilization and reduces amyloid beta-protein secretion

The protein interaction domain of the neuronal protein X11 binds to the YENPTY motif within the cytoplasmic domain of beta-amyloid precursor protein (betaAPP). Amyloid-beta protein (Abeta), the major constituent of the amyloid deposited in brain of Alzheimer's disease patients, is generated by proteolytic processing of betaAPP, which occurs in part following betaAPP internalization. Because the YENPTY motif has a role in the internalization of betaAPP, the effect of X11 binding on betaAPP processing was studied in mouse neuroblastoma N2a, human embryonic kidney 293, monkey kidney COS-1, and human glial U251 cell lines transfected with wild type or mutated betaAPP cDNAs. Secretion of soluble betaAPP via alpha-secretase activity increased significantly in cells transfected with betaAPP variants containing mutations that impair interaction with X11 when compared with cells transfected with wild type cDNA. Cotransfection of betaAPP and X11 caused retention of cellular betaAPP, decreased secretion of sbetaAPPalpha, and decreased Abeta secretion. Thus, betaAPP interaction with the protein interaction domain of X11 stabilizes cellular betaAPP and thereby participates in the regulation of betaAPP processing pathways.

Alzheimer's disease, Kuf's disease, tellurium and selenium

The possible role of the abnormal trace element tellurium in the pathogenesis of Alzheimer's disease is examined. Tellurium has been reported to produce cognitive impairment and cerebral lipofuscinosis in rats-changes akin to those seen in Kuf's disease, a condition which shares certain clinical and neuropathological features with Alzheimer's disease. Tellurium can damage mitochondria; defects in mitochondrial energy metabolism may be relevant to the pathogenesis of neurodegenerative disease. The deficiency of selenium, which may act physiologically as an antagonist of tellurium, in the Alzheimer's disease brain would also be in keeping with the hypothesis of tellurium toxicity as a factor in the pathogenesis of Alzheimer's disease.