Age-associated changes in synaptic lipid raft proteins revealed by two-dimensional fluorescence difference gel electrophoresis

Brain aging is associated with a progressive decline in cognitive function though the molecular mechanisms remain unknown. Functional changes in brain neurons could be due to age-related alterations in levels of specific proteins critical for information processing. Specialized membrane microdomains known as ‘lipid rafts’ contain protein complexes involved in many signal transduction processes. This study was undertaken to determine if two-dimensional fluorescence difference gel electrophoresis (2D DIGE) analysis of proteins in synaptic membrane lipid rafts revealed age-dependent alterations in levels of raft proteins. Five pairs of young and aged rat synaptic membrane rafts were subjected to DIGE separation, followed by image analysis and identification of significantly altered proteins. Of 1046 matched spots on DIGE gels, 94 showed statistically significant differences in levels between old and young rafts, and 87 of these were decreased in aged rafts. The 41 most significantly altered (p < 0.03) proteins included several synaptic proteins involved in energy metabolism, redox homeostasis, and cytoskeletal structure. This may indicate a disruption in bioenergetic balance and redox homeostasis in synaptic rafts with brain aging. Differential levels of representative identified proteins were confirmed by immunoblot analysis. Our findings provide novel pathways in investigations of mechanisms that may contribute to altered neuronal function in aging brain

Identifying Epstein–Barr virus peptide sequences associated with differential IgG antibody response

Background: Epstein-Barr virus (EBV) infection contributes to cancers in a fraction of seropositive individuals, but much remains to be learned about variation in EBV-directed humoral immunity in cancer-free adults. Methods: A protein microarray was used to probe serum from 175 Taiwanese and 141 Northern European adults for immunoglobulin G (IgG) antibody responses to 115 different peptide sequences, representing protein segments or protein variants, from 45 EBV proteins. It was posited that this antibody-based approach could identify EBV peptide sequences representing immunodominant regions relevant for B-cell immunity. Results: Analyses of 45 EBV proteins with multiple protein segments or variants printed on the array identified eight EBV peptide sequences that appear to play a role in immunogenicity. This included: (1) three proteins with segments/regions associated with IgG reactivity (BALF5, LMP1, LMP2A); and (2) five proteins with sequence variants/amino acid changes associated with IgG reactivity (BDLF4, EBNA3A, EBNA3B, EBNA-LP, LF1). Conclusion: This examination of IgG antibody responses against 115 EBV peptide sequences in 316 cancer-free adults represents an important step toward identifying specific EBV protein sequences that play a role in generating B-cell immunity in humans

Low alpha-defensin gene copy number increases the risk for IgA nephropathy and renal dysfunction

IgA nephropathy (IgAN) is the most common primary glomerulonephritis worldwide. Although a major source of genetic variation, copy number variations (CNVs) and their involvement in disease development have not been well studied. Here, we performed association analysis of the DEFA1A3 CNV locus in two independent IgAN cohorts of Southern Chinese Han (total1189 cases and 1187 controls). We discovered three independent copy number associations within the locus: DEFA1A3 (P=3.99×10-9, OR=0.88), DEFA3 (P=6.55×10-5, OR=0.82) and a noncoding deletion variant (211bp) (P=3.50×10-16, OR=0.75) (OR per copy, fixed-effects meta-analysis). While showing strong association with increased risk for IgAN (P=9.56×10-20), low total copy numbers of the three variants also showed significant association with renal dysfunction in patients with IgAN (P=0.03, HR=3.69, after controlling for the effects of known prognostic factors) as well as high serum IgA1 (P=0.02) and a high proportion of galactose-deficient IgA1 (P=0.03). For replication, we confirmed the associations of DEFA1A3 (P=4.42×10-4, OR=0.82) and DEFA3 copy numbers (P=4.30×10-3, OR=0.74) with IgAN in a Caucasian cohort (531 cases and 198 controls) and found the 211bp variant to be much rarer in Caucasians. Interestingly, we also observed an association of the 211bp copy number with membranous nephropathy (P=1.11×10-7, OR=0.74 in 493 Chinese cases and 500 matched controls), but not with diabetic kidney disease (in 806 Chinese cases and 786 matched controls). By explaining 4.96% of disease risk and influencing the renal dysfunction in IgAN, the DEFA1A3 CNV locus is a potential candidate for therapeutic target and prognostic marker development