An antibody to annexin V blocks Ca(2+)-dependent ATPase activity of sarcoplasmic reticulum in human failing hearts

Statistically enhanced spectral counting approach to TCDD cardiac toxicity in the adult zebrafish heart

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a persistent environmental pollutant and teratogen that produces cardiac toxicity in the developing zebrafish. Here we adopted a label free quantitative proteomic approach based on normalized spectral abundance factor (NSAF) to investigate the disturbance of the cardiac proteome induced by TCDD in the adult zebrafish heart. The protein expression level changes between heart samples from TCDD-treated and control zebrafish were systematically evaluated by a large scale MudPIT analysis, which incorporated triplicate analyses for both control and TCDD-exposed heart proteomic samples to overcome the data-dependent variation in shotgun proteomic experiments and obtain a statistically significant protein data set with improved quantification confidence. A total of 519 and 443 proteins were identified in hearts collected from control and TCDD-treated zebrafish, respectively, among which 106 proteins showed statistically significant expression changes. After correcting for the experimental variation between replicate analyses by statistical evaluation, 55 proteins exhibited NSAF ratios above 2 and 43 proteins displayed NSAF ratios smaller than 0.5, with statistical significance by t test (p < 0.05). The proteins identified as altered by TCDD encompass a wide range of biological functions including calcium handling, myocardium cell architecture, energy production and metabolism, mitochondrial homeostasis, and stress response. Collectively, our results indicate that TCDD exposure alters the adult zebrafish heart in a way that could result in cardiac hypertrophy and heart failure and suggests a potential mechanism for the diastolic dysfunction observed in TCDD-exposed embryos.

UDP hydrolase activity associated with the porcine liver annexin fraction

In the crude fraction of porcine liver annexins, we identified annexin IV (AnxIV), AnxII and AnxVI of MW (molecular weight) of 32, 36 and 68 kDa, respectively, an albumin of MW of 61.5 kDa and an UDP hydrolase (UDPase) of MW of 62 kDa, related to the human UDPase from Golgi membranes. The latter enzyme exhibits its highest specificity towards UDP and GDP but not ADP and CDP, and it is stimulated by Mg(2+) and Ca(2+). AnxVI itself, although it binds purine nucleotides, does not exhibit hydrolytic activity towards nucleotides. Taken together, these results suggest that AnxVI may interact in vivo with a nucleotide-utilizing enzyme, UDPase. This is in line with observations made by other investigators that various annexins are able to interact with nucleotide-utilizing proteins, such as protein kinases, GTPases, cytoskeletal proteins and p120(GAP). Such interactions could be of particular importance in modulating the biological activities of these proteins in vivo.

Annexins as nucleotide-binding proteins: facts and speculations

Annexins are ubiquitous multifunctional Ca2+ and phospholipid-binding proteins whose mechanism of function remains largely unknown. The accumulated in vitro experimental evidence indicates that ATP and GTP are functional ligands for nucleotide-sensitive annexin isoforms. Such nucleotide binding could modulate Ca2+ homeostasis, vesicular transport and/or signal transduction pathways and link them to cellular energy metabolism. Alternatively, since annexins are able to interact with other nucleotide-utilizing proteins, such as various kinases, GTPases and structural proteins, these proteins could influence the guanine nucleotide exchange metabolism and/or control the activity of various G proteins. The nucleotide-binding properties of annexins may affect the development or maintenance of some pathologies and diseases in which changes in physiological concentrations of purine nucleotides or disruption of Ca2+ homeostasis are crucial targets.