The human body is in a continuous state of repair and renewal, from breaking down and reusing damaged or excess cell parts via process of autophagy. The endoplasmic reticulum (ER) in the cell cytoplasm, critical to the synthesis and transport of cellular components, is no exception. ER-phagy is a major driver of ER remodelling, and ER-phagy receptors play central roles in this process. Loss-of-function mutations in ER-phagy receptors (FAM134b) result in autosomal recessive hereditary sensory and autonomic neuropathy (HSAN) in humans and dogs.
Within the last decades, several other ER-resident membrane-shaping proteins with central reticulon homology domains (RHD) have been associated with hereditary axonal disorders as well, i.e. ATL1, ATL3, REEP1 and REEP2, SPAST, RTN2, and ARL6IP1. They can also cause hereditary spastic paraplegia/HSP, a neurodegenerative disorder characterized by progressive leg spasticity alone or in combination with loss of sensory and pain perception (HSAN). The underlying mechanisms of pathogenesis of HSP and HSAN neuropathies remain largely elusive. I will discuss the role of multiple ER-phagy receptors and post-translational modifications in controlling efficient ER remodelling and renewal. Defects along the ER-phagy pathways contribute to the development of neuropathies.