Protein phosphatase-1 (PP1) plays a key role in dephosphorylation in numerous biological processes such as glycogen metabolism, cell cycle regulation, smooth muscle contraction, and protein synthesis. Microorganisms produce a variety of inhibitors of PP1, which include the microcystin class of inhibitors and okadaic acid, the latter being the major cause of diarrhetic shellfish poisoning and a powerful tumor promoter. We have determined the crystal structure of the molecular complex of okadaic acid bound to PP1 to a resolution of 1.9 Å. This structure reveals that the acid binds in a hydrophobic groove adjacent to the active site of the protein and interacts with basic residues within the active site. Okadaic acid exhibits a cyclic structure, which is maintained via an intramolecular hydrogen bond. This is reminiscent of other macrocyclic protein phosphatase inhibitors. The inhibitor-bound enzyme shows very little conformational change when compared with two other PP1 structures, except in the inhibitor-sensitive ␤12-␤13 loop region. The selectivity of okadaic acid for protein phosphatases-1 and -2A but not PP-2B (calcineurin) may be reassessed in light of this study.The phosphorylation and dephosphorylation of proteins is vital to the regulation of many cellular pathways and processes. Two classes of enzymes in the cell that catalyze cellular dephosphorylation activity are tyrosine phosphatases and serine/threonine phosphatases (1). Classification of serine/threonine phosphatases can be subdivided into four categories: protein phosphatase-1 (PP1), 1 -2A (PP2A), -2B(PP2B) and -2C (PP2C) (2). The first three of these categories comprise what is known as the PPP family of protein phosphatases since they contain extensive sequence similarity in their catalytic domains and little or no sequence homology to PP2C or to tyrosine phosphatases. There are several natural toxin inhibitors of the PPP family of enzymes. These include microcystins, calyculins, tautomycin and okadaic acid (OA) ( Fig. 1) (1).OA is a tumor-promoting C 38 polyether fatty acid produced by marine dinoflagellates (1, 3-6). OA contains acidic and hydrophobic moieties and is cyclic (via an intramolecular hydrogen bond) (6). This toxin can accumulate in filter-feeding organisms and is the principle cause of diarrhetic shellfish poisoning worldwide (4).There have been many biochemical and modeling studies on the inhibition of the PPP family of phosphatases by the natural toxins, but the lone crystal structure is of microcystin-LR (MCLR) bound to PP1 (␣ isoform) (8). Here we describe the crystal structure of OA bound to the recombinant catalytic subunit of PP1 (␥ isoform). EXPERIMENTAL PROCEDURESCrystallization-The catalytic subunit of protein phosphatase-1 ␥ isoform was purified as described previously (9, 10). OA was purified from Prorocentrum lima (9, 10). Crystals were obtained by the hanging drop vapor diffusion method at room temperature. The enzyme and inhibitor were mixed in a 1:2 molar ratio with the concentration of protein being ϳ0.4 mM. The P...

Anti-DSG2 antibodies are a sensitive and specific biomarker for ARVC. The development of autoimmunity as a result of target-related mutations is unique. Anti-DSG2 antibodies likely explain the cardiac inflammation that is frequently identified in ARVC and may represent a new therapeutic target.

Background It is unclear whether exposure to surgery in early life has long-term adverse effects on child development. The authors aimed to investigate whether surgery in early childhood is associated with adverse effects on child development measured at primary school entry. Methods The authors conducted a population-based cohort study in Ontario, Canada, by linking provincial health administrative databases to children’s developmental outcomes measured by the Early Development Instrument (EDI). From a cohort of 188,557 children, 28,366 children who underwent surgery before EDI completion (age 5 to 6 yr) were matched to 55,910 unexposed children. The primary outcome was early developmental vulnerability, defined as any domain of the EDI in the lowest tenth percentile of the population. Subgroup analyses were performed based on age at first surgery (less than 2 and greater than or equal to 2 yr) and frequency of surgery. Results Early developmental vulnerability was increased in the exposed group (7,259/28,366; 25.6%) compared with the unexposed group (13,957/55,910; 25.0%), adjusted odds ratio, 1.05; 95% CI, 1.01 to 1.08. Children aged greater than or equal to 2 yr at the time of first surgery had increased odds of early developmental vulnerability compared with unexposed children (odds ratio, 1.05; 95% CI, 1.01 to 1.10), but children aged less than 2 yr at the time of first exposure were not at increased risk (odds ratio, 1.04; 95% CI, 0.98 to 1.10). There was no increase in odds of early developmental vulnerability with increasing frequency of exposure. Conclusions Children who undergo surgery before primary school age are at increased risk of early developmental vulnerability, but the magnitude of the difference between exposed and unexposed children is small.