Moonlighting proteins induce protection in a mouse model against Candida species.

In recent years, C. albicans and C. glabrata have been identified as the main cause of candidemia and invasive candidiasis in hospitalized and immunocompromised patients. In order to colonize the human host, these fungi express several virulence factors such as the response to oxidative stress and the formation of biofilms. In the expression of these virulence factors, the cell wall of C. albicans and C. glabrata is of fundamental importance. As the outermost structure of the yeast, the cell wall is the first to come in contact with the reactive oxygen species (ROS) generated during the respiratory outbreak, and in the formation of biofilms, it is the first to adhere to organs or medical devices implanted in the human host. In both processes, several cell wall proteins (CWP) are required, since they promote attachment to human cells or abiotic surfaces, as well as to detoxify ROS. In our working group we have identified moonlighting CWP in response to oxidative stress as well as in the formation of biofilms. Having identified moonlighting CWP in Candida species in response to two virulence factors indicates that these proteins may possibly be immunodominant. The aim of the present work was to evaluate whether proteins of this type such as fructose-bisphosphate aldolase (Fba1), phosphoglycerate kinase (Pgk) and pyruvate kinase (Pk), could confer protection in a mouse model against C. albicans and C. glabrata. For this, recombinant proteins His6-Fba1, His6-Pgk and His6-Pk were constructed and used to immunize several groups of mice. The immunized mice were infected with C. albicans or C. glabrata, and subsequently the liver, spleen and kidney were extracted and the number of CFU was determined. Our results showed that Pk confers immunity to mice against C. albicans, while Fba1 to C. glabrata. This data allows us to conclude that the moonlighting CWP, Fba1 and Pk confer in vivo protection in a specific way against each species of Candida. This makes them promising candidates for developing specific vaccines against these pathogens.

Recovery of motor function of chronic spinal cord injury by extracellular pyruvate kinase isoform M2 and the underlying mechanism.

In our previous study, we found that pyruvate kinase isoform M2 (PKM2) was secreted from the skeletal muscle and extended axons in the cultured neuron. Indirect evidence suggested that secreted PKM2 might relate to the recovery of motor function in spinal cord injured (SCI) mice. However, in vivo direct evidence has not been obtained, showing that extracellular PKM2 improved axonal density and motor function in SCI mice. In addition, the signal pathway of extracellular PKM2 underlying the increase in axons remained unknown. Therefore, this study aimed to identify a target molecule of extracellular PKM2 in neurons and investigate the critical involvement of extracellular PKM2 in functional recovery in the chronic phase of SCI. Recombinant PKM2 infusion to the lateral ventricle recovered motor function in the chronic phase of SCI mice. The improvement of motor function was associated with axonal increase, at least of raphespinal tracts connecting to the motor neurons directly or indirectly. Target molecules of extracellular PKM2 in neurons were identified as valosin-containing protein (VCP) by the drug affinity responsive target stability method. ATPase activation of VCP mediated the PKM2-induced axonal increase and recovery of motor function in chronic SCI related to the increase in axonal density. It is a novel finding that axonal increase and motor recovery are mediated by extracellular PKM2-VCP-driven ATPase activity.