The pathogenesis of motor neuron and muscle dysfunction in spinal muscular atrophy (SMA), a leading genetic cause of infant mortality, is still unresolved. SMA results from low levels of the Survival Motor Neuron SMN protein. The rationale underlying these experiments is our discovery that the SMN protein binds to and moves in neurons together with the CopA protein, the largest constituent of the heptameric COPI coatomer complex. The objective of this proposal is to determine the molecular mechanisms by which reduced SMN interaction with COPI complex and loss of COPI activities leads to neurodegeneration. Golgi-derived COPI vesicles are necessary for post-translational processing and transport of proteins and other cargoes between Golgi apparatus and endoplasmic reticulum and secretory pathway. Golgi alterations have been observed in SMA, amyotrophic lateral sclerosis, Alzheimer?s disease, and other neurodegenerative disorders. Our data demonstrate that pathologically low levels of SMN alter the morphology and functionality of the Golgi apparatus. The overall premise of this proposal is that the COPI complex is necessary for processing and trafficking of cargoes essential for normal motor neuron maintenance. We have also shown that specific mRNAs are found in association with COPI. One class of cargo emphasized in this grant is mRNA selected for axonal transport. We propose genetic, biochemical, proteomic and transgenic approaches to define the properties and activities of the COPI complex and its interactions with SMN and other potential binding partners. We will create murine models to investigate the role of COPI in the neuron and perform correlative in vivo studies of axonogenesis, RNA trafficking and pathologic biological outcomes. Because SMN physically interacts with factors linked to other neurodegenerative diseases, thereby implicating commonality of causality, these experiments should result in new insights into the aberrant processes occurring in these disorders. Moreover, pharmacologic induction of the COPI pathway may represent a novel objective for treatment of SMA and other neurodegenerative diseases.

Public Health Relevance

The protein SMN is deficient in spinal muscular atrophy (SMA) and binds to and moves with COPI, a multi- functional complex responsible for protein processing and movement within the cell. We will undertake detailed investigations of this transport pathway, focusing on its relationship to SMA and how it delivers vital cargoes throughout the nerve cell. We will create novel mouse models to learn what goes wrong in SMA and other nerve and muscle diseases.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
2R01NS082284-06A1
Application #
9817728
Study Section
Cell Death in Neurodegeneration Study Section (CDIN)
Program Officer
Nuckolls, Glen H
Project Start
2013-08-15
Project End
2024-04-30
Budget Start
2019-05-15
Budget End
2020-04-30
Support Year
6
Fiscal Year
2019
Total Cost
Indirect Cost
Name
Indiana University-Purdue University at Indianapolis
Department
Dermatology
Type
Schools of Medicine
DUNS #
603007902
City
Indianapolis
State
IN
Country
United States
Zip Code
46202
Custer, Sara K; Foster, Joycelynn N; Astroski, Jacob W et al. (2018) Abnormal Golgi morphology and decreased COPI function in cells with low levels of SMN. Brain Res :
Khairallah, Marie-Therese; Astroski, Jacob; Custer, Sarah K et al. (2017) SMN deficiency negatively impacts red pulp macrophages and spleen development in mouse models of spinal muscular atrophy. Hum Mol Genet 26:932-941
Custer, Sara K; Gilson, Timra D; Li, Hongxia et al. (2016) Altered mRNA Splicing in SMN-Depleted Motor Neuron-Like Cells. PLoS One 11:e0163954
Li, Hongxia; Custer, Sara K; Gilson, Timra et al. (2015) ?-COP binding to the survival motor neuron protein SMN is required for neuronal process outgrowth. Hum Mol Genet 24:7295-307
Custer, Sara K; Androphy, Elliot J (2014) Autophagy dysregulation in cell culture and animals models of spinal muscular atrophy. Mol Cell Neurosci 61:133-40
Todd, Adrian G; Lin, Hai; Ebert, Allison D et al. (2013) COPI transport complexes bind to specific RNAs in neuronal cells. Hum Mol Genet 22:729-36
Custer, Sara K; Todd, Adrian G; Singh, Natalia N et al. (2013) Dilysine motifs in exon 2b of SMN protein mediate binding to the COPI vesicle protein ?-COP and neurite outgrowth in a cell culture model of spinal muscular atrophy. Hum Mol Genet 22:4043-52
Peter, Cyril Jayakumar; Evans, Matthew; Thayanithy, Venugopal et al. (2011) The COPI vesicle complex binds and moves with survival motor neuron within axons. Hum Mol Genet 20:1701-11