Mechanistic insights into the interaction of the MOG1 protein with the cardiac sodium channel Nav1.5 clarify the molecular basis of Brugada syndrome

Abstract

Edited by Mike ShipstonNa v 1.5 is the ␣-subunit of the cardiac sodium channel complex. Abnormal expression of Na v 1.5 on the cell surface because of mutations that disrupt Na v 1.5 trafficking causes Brugada syndrome (BrS), sick sinus syndrome (SSS), cardiac conduction disease, dilated cardiomyopathy, and sudden infant death syndrome. We and others previously reported that Ran-binding protein MOG1 (MOG1), a small protein that interacts with Na v 1.5, promotes Na v 1.5 intracellular trafficking to plasma membranes and that a substitution in MOG1, E83D, causes BrS. However, the molecular basis for the MOG1/Nav1.5 interaction and how the E83D substitution causes BrS remains unknown. Here, we assessed the effects of defined MOG1 deletions and alanine-scanning substitutions on MOG1's interaction with Na v 1.5. Large deletion analysis mapped the MOG1 domain required for the interaction with Na v 1.5 to the region spanning amino acids 146 -174, and a refined deletion analysis further narrowed this domain to amino acids 146 -155. Site-directed mutagenesis further revealed that Asp-148, Arg-150, and Ser-151 cluster in a peptide loop essential for binding to Na v 1.5. GST pulldown and electrophysiological analyses disclosed that the substitutions E83D, D148Q, R150Q, and S151Q disrupt MOG1's interaction with Na v 1.5 and significantly reduce its trafficking to the cell surface. Examination of MOG1's 3D structure revealed that Glu-83 and the loop containing Asp-148, Arg-150, and Ser-151 are spatially proximal, suggesting that these residues form a critical binding site for Na v 1.5. In conclusion, our findings identify the structural elements in MOG1 that are crucial for its interaction with Na v 1.5 and improve our understanding of how the E83D substitution causes BrS. 3 The abbreviations used are: BrS, Brugada syndrome; SSS, sick sinus syndrome; aa, amino acid; GST-Na v 1.5-LII, GST-Na v 1.5-loop II.

Mog1 knockout causes cardiac hypertrophy and heart failure by downregulating tbx5‐cryab‐hspb2 signalling in zebrafish

“…The isolated zebrafish cardiomyocytes were used for whole cell voltage clamping recordings of sodium currents as described previously 13,21,31,32 . Electrode resistance ranged from 2 to 3 MΩ when filled with the pipette solution containing 20 mmol/L NaCl, 130 mmol/L CsCl, 10 mmol/L EGTA and 10 mmol/L HEPES (pH 7.2 adjust with CsOH).…”

Inherited and Acquired Rhythm Disturbances in Sick Sinus Syndrome, Brugada Syndrome, and Atrial Fibrillation: Lessons from Preclinical Modeling

“…They proved that E83D-inducing mutation impaired the specific binding of the two proteins, consequently producing a trafficking defect of Nav1.5 channels. This translated in no effects on their transcription but caused an important I Na reduction [240].…”

“…MOG1 overexpression could be to induce a rescue, even in case of SCN5A mutation [239,240] Unknown gene mutations…”

Life Cycle of the Cardiac Voltage-Gated Sodium Channel NaV1.5

“…MOG1 is found to interact with Ran GTP, a small protein that mediates the nucleus import and export of proteins and RNA ( Steggerda and Paschal, 2001 ). MOG1 is shown to promote intracellular trafficking of Na V 1.5 from the ER ( Yu et al, 2018 ). Thus, MOG1 may also play a regulatory role in the nucleus-cytoplasmic trafficking of SCN5A mRNA.…”

“…COPII-coated vesicles in association with Sec23/24, Sec13/31, Sar1, and Sec12 mediate anterograde protein trafficking between the ER and Golgi ( Kurokawa and Nakano, 2019 ). MOG1 facilitates the export of Na V 1.5 from the ER and improves Na V 1.5 expression on the cell surface, probably by interacting with Sar1A and Sar1B ( Chakrabarti et al, 2013 ; Wang et al, 2018 ; Yu et al, 2018 ; Kurokawa and Nakano, 2019 ). It is now recognized that ER retention signals can also play an important role in ER export of many plasma membrane proteins.…”