Association of Calcineurin with the COPI Protein Sec28 and the COPII Protein Sec13 Revealed by Quantitative Proteomics

Calcineurin is a calcium-calmodulin-dependent serine/threonine specific protein phosphatase operating in key cellular processes governing responses to extracellular cues. Calcineurin is essential for growth at high temperature and virulence of the human fungal pathogen Cryptococcus neoformans but the underlying mechanism is unknown. We performed a mass spectrometry analysis to identify proteins that associate with the calcineurin A catalytic subunit (Cna1) in C. neoformans cells grown under non-stress and high temperature stress conditions. A novel prioritization strategy for mass spectrometry data from immunoprecipitation experiments identified putative substrates and proteins potentially operating with calcineurin in common pathways. Cna1 co-purified with proteins involved in membrane trafficking including the COPI component Sec28 and the COPII component Sec13. The association of Cna1 with Sec28 and Sec13 was confirmed by co-immunoprecipitation. Cna1 exhibited a dramatic change in subcellular localization during high temperature stress from diffuse cytoplasmic to ER-associated puncta and the mother-bud neck and co-localized with Sec28 and Sec13

Implications of the functional anatomy of the hand and forearm of Ailurus fulgens (Carnivora, Ailuridae) for the evolution of the ‘false-thumb’ in pandas

Both the giant panda (Ailuropoda melanoleuca) and the red panda (Ailurus fulgens) possess a ‘false-thumb’, actually an enlarged radial sesamoid bone, which contributes to the gripping action of the hand. These species are not closely related, however, as one is an ursid and the other an ailurid, so the fact that they share this adaptation implies a remarkable convergence. We studied the functional anatomy of this structure in the red panda, comparing it with existing descriptions of the grasping mechanism in both pandas. Previous interpretations of the radial sesamoid in Ailurus as a rod-like structure without direct articulation to the wrist bones are inaccurate. There are various important differences between the red panda and the giant panda. In the former, the lesser development of the radial sesamoid, its connection with the flexor retinaculum, the presence of an insertion of the muscle abductor pollicis longus in the first metacarpal, which enhances its supinatory action, and the presence of a muscle flexor brevis digitorum manus point to thin-branch climbing features serving as an exaptation to the more recent role of the red panda hand in the manipulation of bamboo