ATXN2 and Machado-Joseph disease: Abnormal levels of glutamatergic receptors and/or transporters have been described in cellular and animal models of SCA1 [233, 312], SCA2 [296, 313], SCA3/MJD [302, 313, 314] and SCA6 [315], impacting intracellular Ca2+ levels and Ca2+-binding protein activation.