Dynactin p150Glued–Deficiency in Midbrain Dopaminergic Neurons Leads to Progressive Neurodegeneration and Endoplasmic Reticulum Dysfunction

Background Multiple missense mutations in DCTN1 gene have been linked to Perry syndrome (PS), a rare neurodegenerative disease clinically manifested with parkinsonism, mental depression, and central hypoventilation. DCTN1 encodes dynactin p150Glued protein, the largest subunit of dynactin motor protein complex. The PS-related mutations are concentrated at the amino-terminal cytoskeleton-associated protein and glycine-rich (CAP-Gly) domain, which mediates the association of p150Glued with microtubules. Degeneration of nigrostriatal dopaminergic neurons (DANs) was reported in the postmortem brains of PS patients. However, how the dysfunction of p150Glued affects the function and survival of DANs remains to be determined. Methods Using Cre-LoxP genetic manipulation, we crossbred Dctn1 knock-in (KI) mice with Th-Cre mice to generate Dctn1 conditional knockout (cKO) mice for genetic deletion of p150Glued protein in catecholaminergic neurons, including midbrain DANs. We also crossbred the Dctn1 KI mice with Cre/Esr1 mice to generate pups for primary culture of Dctn1 cKO cells. We then performed series of biochemical, neurochemical, cell biology, behavioral and neuropathological studies on the Dctn1 cKO mice or cells to investigate the underlying pathological mechanisms. Results While both Dctn1 control and cKO mice showed deterioration of rotarod motor performance during aging, the process was greatly accelerated in the cKO mice. The loss of p150Glued led to progressive degeneration of axon fibers and then cell bodies of midbrain DANs. In addition to neurodegeneration, abnormal accumulation of a-synuclein was found in the soma and nuclei of DANs in aged cKO mice. Moreover, before the onset of axon atrophy, both dopamine transporter (DAT) levels and activity were reduced in the DAN axon terminals of cKO mice. Further studies revealed unusually large spheric structures in the axons and dendrites of cKO DANs. Interestingly, endoplasmic reticulum (ER) stress protein BiP was abnormally accumulated in the dendritic spheroids and soma of cKO DANs. Accordingly, the Dctn1 cKO cells displayed impaired ER export and increased unfolded protein response (UPR). As a result, the Dctn1 cKO DANs were more vulnerable to ER stress-induced cell death. Conclusion Our findings demonstrate that p150Glued is important in maintaining the function and survival of midbrain DANs during aging. We particularly highlighted the role of p150Glued in stabilizing the molecular machinery for ER export, suggesting that the PS-related p150Glued dysfunction may render the midbrain DANs more susceptible to UPR and ER stress.