Is GSK3ß a molecular target of chloroquine treatment against COVID-19?

The recent clinical trial reports pertaining to the efficacy of chloroquine and hydroxychloroquine against COVID-19 albeit yet to be validated with larger clinical trials, have sparked much interest globally to evaluate whether this anti-malarial drug can be repurposed for the treatment of COVID-19. In addition to its anti-viral activity, the anti-inflammatory activity of chloroquine may also contribute to its efficacy. Based on our data obtained from an animal infection model of melioidosis (a disease caused by the bacteria Burkholderia pseudomallei), treatment with chloroquine can result in the phosphorylation and consequent inhibition of glycogen synthase kinase-3ß (GSK3ß). This serine/threonine protein kinase is now recognised as a point of convergence for host inflammatory response. In view of this, it is plausible that the mechanism for the anti-inflammatory effect of chloroquine against COVID-19 involves inhibition of host GSK3ß.

Phosphorylated and Nonphosphorylated PfMAP2 Are Localized in the Nucleus, Dependent on the Stage of Plasmodium falciparum Asexual Maturation.

Plasmodium falciparum mitogen-activated protein (MAP) kinases, a family of enzymes central to signal transduction processes including inflammatory responses, are a promising target for antimalarial drug development. Our study shows for the first time that the P. falciparum specific MAP kinase 2 (PfMAP2) is colocalized in the nucleus of all of the asexual erythrocytic stages of P. falciparum and is particularly elevated in its phosphorylated form. It was also discovered that PfMAP2 is expressed in its highest quantity during the early trophozoite (ring form) stage and significantly reduced in the mature trophozoite and schizont stages. Although the phosphorylated form of the kinase is always more prevalent, its ratio relative to the nonphosphorylated form remained constant irrespective of the parasites' developmental stage. We have also shown that the TSH motif specifically renders PfMAP2 genetically divergent from the other plasmodial MAP kinase activation sites using Neighbour Joining analysis. Furthermore, TSH motif-specific designed antibody is crucial in determining the location of the expression of the PfMAP2 protein. However, by using immunoelectron microscopy, PPfMAP2 were detected ubiquitously in the parasitized erythrocytes. In summary, PfMAP2 may play a far more important role than previously thought and is a worthy candidate for research as an antimalarial.