MAPK3 and myalgic encephalomeyelitis/chronic fatigue syndrome: Impaired Ca2+ signalling in NK cells from CFS/ME patients has been demonstrated through changes to ERK1/2 and mitogen-activated protein kinase (MAPK) pathways (Chacko et al., 2016; Huth et al., 2016), as these components are activated in a Phosphatidylinositol-4,5-bisphosphate 3-kinase (P13K)-dependent manner that may also be associated with cytoplasmic Ca2+ ion levels through activation of TRPM3 (Lee et al., 2003).