SPAST and Spastic paraplegia: REEP proteins are tethered to the cytoplasmic face of the endoplasmic reticulum (ER) and contiguous membranes, and are implicated in ER morphology (as are the other hereditary spastic paraplegia proteins atlastin and spastin), mitochondrial function, and translocation of olfactory, taste and other receptors to the cell surface [33,34].