Lysine Distinctively Manipulates Myogenic Regulatory Factors and Wnt/Ca2+ Pathway in Slow and Fast Muscles, and Their Satellite Cells of Postnatal Piglets.

Muscle regeneration, representing an essential homeostatic process, relies mainly on the myogenic progress of resident satellite cells, and it is modulated by multiple physical and nutritional factors. Here, we investigated how myogenic differentiation-related factors and pathways respond to the first limiting amino acid lysine (Lys) in the fast and slow muscles, and their satellite cells (SCs), of swine. Thirty 28-day-old weaned piglets with similar body weights were subjected to three diet regimens: control group (d 0-28: 1.31% Lys, n = 12), Lys-deficient group (d 0-28: 0.83% Lys, n = 12), and Lys rescue group (d 0-14: 0.83% Lys; d 15-28: 1.31% Lys, n = 6). Pigs on d 15 and 29 were selectively slaughtered for muscular parameters evaluation. Satellite cells isolated from fast (semimembranosus) and slow (semitendinosus) muscles were also selected to investigate differentiation ability variations. We found Lys deficiency significantly hindered muscle development in both fast and slow muscles via the distinct manipulation of myogenic regulatory factors and the Wnt/Ca2+ pathway. In the SC model, Lys deficiency suppressed the Wnt/Ca2+ pathways and myosin heavy chain, myogenin, and myogenic regulatory factor 4 in slow muscle SCs but stimulated them in fast muscle SCs. When sufficient Lys was attained, the fast muscle-derived SCs Wnt/Ca2+ pathway (protein kinase C, calcineurin, calcium/calmodulin-dependent protein kinase II, and nuclear factor of activated T cells 1) was repressed, while the Wnt/Ca2+ pathway of its counterpart was stimulated to further the myogenic differentiation. Lys potentially manipulates the differentiation of porcine slow and fast muscle myofibers via the Wnt/Ca2+ pathway in opposite trends.

A novel method for concentration of porcine reproductive and respiratory syndrome virus from the environmental samples using self-aggregating peptide-tagged CD151-binding capture.

Environmental surveillance of porcine reproductive and respiratory syndrome virus (PRRSV) represents a key issue in control of the disease. CD151 has recently been recognized as one of several receptors for PRRSV. We describe here a novel method for concentration of PRRSV from the environmental samples by CD151-binding capture. After fusion to self-aggregating peptide ELK16, the large extracellular loop (LEL) of porcine CD151 and its two segments (namely N63 and C63) were expressed in E. coli as protein aggregates. The three fusion proteins were purified to high purities by regular centrifugation and washing with Triton X-100. Viral binding assay showed that the C63-ELK16 protein, but not ELK16-N63 protein, had the specific binding affinity for PRRSV. The C63-ELK16 protein could bind to, and eluted from, PRRSV in pH-, temperature-, and time-dependent manners with a final virus recovery of 44.7%. By using PRRSV-spiked and experimentally infected pig fecal slurry samples, the C63-ELK16 binding capture-combined quantitative RT-PCR was shown to have higher detection sensitivity than the conventional RT-PCR. Although the viral RNA could be detected in the experimentally infected pig samples with or without C63-ELK16 binding capture, infectious PRRSV was not isolated without C63-ELK16 binding capture. Therefore, the CD151-binding capture method established offers sufficient recovery and quickness and will facilitate environmental PRRSV surveillance.