Dysbindin as a novel biomarker for pancreatic ductal adenocarcinoma identified by proteomic profiling.

Pancreatic adenocarcinoma (PDAC) is known to have a poor prognosis partly because of lack of effective biomarkers. In the test set, we investigated dysbindin (DTNBP1) as a potential biomarker for PDAC by comparing preoperative and postoperative serum mass spectrometry (MS) proteomic profilings. Of the included 50 PDAC patients, 42 (positivity of 84.0%) detected a lower MS peak in postoperative serums than preoperative ones which was then identified as dysbindin. In the verification set, receiver operating characteristics (ROC) were used to assess diagnostic efficiency. 550 participants were included in the verification set [250 with PDAC, 80 with benign biliary obstruction (BBO), 70 with chronic pancreatitis (CP) and 150 healthy donors (HD)]. Dysbindin was increased in PDAC patient sera than in all controls. ROC curves revealed the optimum diagnostic cutoff for dysbindin was 699.16 pg/ml [area under curve (AUC) 0.849 (95% CI 0.812-0.885), sensitivity 81.9% and specificity 84.7%]. Raised concentration of dysbindin in sera could differentiate PDAC from BBO, CP and HD. Moreover, dysbindin maintained its diagnostic accuracy for PDAC patients who were CA19-9 negative [AUC 0.875 (95% CI 0.804-0.945), sensitivity 83.0%, specificity 89.0%] and for patients with benign biliary obstruction [AUC 0.849 (95% CI 0.803-0.894), sensitivity 82.3%, specificity 84.0%].Our discovery of dysbindin may complement measurement of CA19-9 in the diagnosis of PDAC and help to discriminate PDAC from other pancreatic diseases or begin biliary obstruction.

Muscle structure influences utrophin expression in mdx mice.

Duchenne muscular dystrophy (DMD) is a severe muscle wasting disorder caused by mutations in the dystrophin gene. To examine the influence of muscle structure on the pathogenesis of DMD we generated mdx4cv:desmin double knockout (dko) mice. The dko male mice died of apparent cardiorespiratory failure at a median age of 76 days compared to 609 days for the desmin-/- mice. An ∼ 2.5 fold increase in utrophin expression in the dko skeletal muscles prevented necrosis in ∼ 91% of 1a, 2a and 2d/x fiber-types. In contrast, utrophin expression was reduced in the extrasynaptic sarcolemma of the dko fast 2b fibers leading to increased membrane fragility and dystrophic pathology. Despite lacking extrasynaptic utrophin, the dko fast 2b fibers were less dystrophic than the mdx4cv fast 2b fibers suggesting utrophin-independent mechanisms were also contributing to the reduced dystrophic pathology. We found no overt change in the regenerative capacity of muscle stem cells when comparing the wild-type, desmin-/-, mdx4cv and dko gastrocnemius muscles injured with notexin. Utrophin could form costameric striations with α-sarcomeric actin in the dko to maintain the integrity of the membrane, but the lack of restoration of the NODS (nNOS, α-dystrobrevin 1 and 2, α1-syntrophin) complex and desmin coincided with profound changes to the sarcomere alignment in the diaphragm, deposition of collagen between the myofibers, and impaired diaphragm function. We conclude that the dko mice may provide new insights into the structural mechanisms that influence endogenous utrophin expression that are pertinent for developing a therapy for DMD.

Expression of multiple AQP4 pools in the plasma membrane and their association with the dystrophin complex.

Altered aquaporin-4 (AQP4) expression has been reported in brain edema, tumors, muscular dystrophy, and neuromyelitis optica. However, the plasma membrane organization of AQP4 and its interaction with proteins such as the dystrophin-associated protein complex are not well understood. In this study, we used sucrose density gradient ultracentrifugation and 2D blue native/sodium dodecyl sulfate-polyacrylamide gel electrophoresis and showed the expression of several AQP4 multi-subunit complexes (pools) of different sizes, ranging from >> 1 MDa to approximately 500 kDa and containing different ratios of the 30/32 kDa AQP4 isoforms, indicative of orthogonal arrays of particles of various sizes. A high molecular weight pool co-purified with dystrophin and beta-dystroglycan and was drastically reduced in the skeletal muscle of mdx3cv mice, which have no dystrophin. The number and size of the AQP4 pools were the same in the kidney where dystrophin is not expressed, suggesting the presence of dystrophin-like proteins for their expression. We found that AQP2 is expressed only in one major pool of approximately 500 kDa, indicating that the presence of different pools is a peculiarity of AQP4 rather than a widespread feature in the AQP family. Finally, in skeletal muscle caveolin-3 did not co-purify with any AQP4 pool, indicating the absence of interaction of the two proteins and confirming that caveolae and orthogonal arrays of particles are two independent plasma membrane microdomains. These results contribute to a better understanding of AQP4 membrane organization and raise the possibility that abnormal expression of specific AQP4 pools may be found in pathological states.