HTT and Huntington disease: Supporting the view that reduced calcineurin may be neuroprotective in HD, increased Htt phosphorylation can be produced by pharmacological inhibition of calcineurin with the immunosuppressor FK506 (also known as tacrolimus and fujimycine) (Pardo et al., 2006), or by overexpression of the regulators of calcineurin RCAN1-1L (Ermak et al., 2009) leading to neuroprotective effects.