Nucleoporin POM121 signals TFEB-mediated autophagy via activation of SIGMAR1/sigma-1 receptor chaperone by pridopidine

ABSTRACT

Macroautophagy/autophagy is an essential process for cellular survival and is implicated in many diseases. A critical step in autophagy is the transport of the transcription factor TFEB from the cytosol into the nucleus, through the nuclear pore (NP) by KPNB1/importinβ1. In the C9orf72 subtype of amyotrophic lateral sclerosis-frontotemporal lobar degeneration (ALS-FTD), the hexanucleotide (G4C2)RNA expansion (HRE) disrupts the nucleocytoplasmic transport of TFEB, compromising autophagy. Here we show that a molecular chaperone, the SIGMAR1/Sigma-1 receptor (sigma non-opioid intracellular receptor 1), facilitates TFEB transport into the nucleus by chaperoning the NP protein (i.e., nucleoporin) POM121 which recruits KPNB1. In NSC34 cells, HRE reduces TFEB transport by interfering with the association between SIGMAR1 and POM121, resulting in reduced nuclear levels of TFEB, KPNB1, and the autophagy marker LC3-II. Overexpression of SIGMAR1 or POM121, or treatment with the highly selective and potent SIGMAR1 agonist pridopidine, currently in phase 2/3 clinical trials for ALS and Huntington disease, rescues all of these deficits. Our results implicate nucleoporin POM121 not merely as a structural nucleoporin, but also as a chaperone-operated signaling molecule enabling TFEB-mediated autophagy. Our data suggest the use of SIGMAR1 agonists, such as pridopidine, for therapeutic development of diseases in which autophagy is impaired.

Abbreviations: ALS-FTD, amyotrophic lateral sclerosis-frontotemporal dementiaC9ALS-FTD, C9orf72 subtype of amyotrophic lateral sclerosis-frontotemporal dementiaCS, citrate synthaseER, endoplasmic reticulumGSS, glutathione synthetaseHRE, hexanucleotide repeat expansionHSPA5/BiP, heat shock protein 5LAMP1, lysosomal-associated membrane protein 1MAM, mitochondria-associated endoplasmic reticulum membraneMAP1LC3/LC3, microtubule-associated protein 1 light chain 3NP, nuclear poreNSC34, mouse motor neuron-like hybrid cell lineNUPs, nucleoporinsPOM121, nuclear pore membrane protein 121SIGMAR1/Sigma-1R, sigma non-opioid intracellular receptor 1TFEB, transcription factor EBTMEM97/Sigma-2R, transmembrane protein 97

KEYWORDS:

• ALS/FTD
• c9orf72
• chaperone
• KPNB1/importinβ1
• nucleocytoplasmic transport
• nucleoporin POM121
• pridopidine
• SIGMAR1
• sigma-1 receptor
• TFEB

Acknowledgments

We thank Amy Newman for suggestions and Kenner Rice of NIDA for the supply of BD1063∙HBr. We thank Adrian Isaacs of University College of London for the gift of the (G4C2)₁₆₆ and (G4C2)₂₈₈ vectors. We thank Tzyy-Choou Wu of Johns Hopkins Medical School for advice on paraffin embedding of culture cells. We thank Noga Gershoni, Jamie L. Weiss, and Mary Pfeiffer for the editing of this manuscript. This report was supported in part by the Intramural Research Program of the National Institute on Drug Abuse, NIH, DHHS.

Disclosure statement

SMW, HEW, MC, TPS have no conflict of financial interest in the publication of this manuscript. MRH is CEO of Prilenia Neurotherapeutics, BV. MG is an employee of Prilenia Neurotherapeutics, Ltd, a subsidiary of Prilenia Therapeutics, BV. TM holds patents describing SIGMAR1/Sig1R ligands and did consultancies for Prilenia Therapeutics. TPS served from March, 2019- March, 2020, per NIDA/NIH approval, as a non-paid member of the Advisory Board to the Prilenia Therapeutics.

Subject classification

Neuroscience

Materials and data availability

All materials requests and correspondence are to be addressed to the corresponding author, Dr. Tsung-Ping Su. All original data are available upon reasonable request.

Supplementary material

Supplemental data for this article can be accessed here.

Additional information

Funding

This work was supported by the National Institute on Drug Abuse [DA000206-35].