Cohesin-protein Shugoshin-1 controls cardiac automaticity via HCN4 pacemaker channel

Abstract

Endogenous cardiac pacemaker function regulates the rate and rhythm of cardiac contraction. The mutation p.Lys23Glu in the cohesin protein Shugoshin-1 causes severe heart arrhythmias due to sinoatrial node dysfunction and a debilitating gastrointestinal motility disorder, collectively termed the Chronic Atrial and Intestinal Dysrhythmia Syndrome, linking Shugoshin-1 and pacemaker activity. Hyperpolarization-activated, cyclic nucleotide-gated cation channel 4 (HCN4) is the predominant pacemaker ion-channel in the adult heart and carries the majority of the “funny” current, which strongly contributes to diastolic depolarization in pacemaker cells. Here, we study the mechanism by which Shugoshin-1 affects cardiac pacing activity with two cell models: neonatal rat ventricular myocytes and Chronic Atrial and Intestinal Dysrhythmia Syndrome patient-specific human induced pluripotent stem cell derived cardiomyocytes. We find that Shugoshin-1 interacts directly with HCN4 to promote and stabilize cardiac pacing. This interaction enhances funny-current by optimizing HCN4 cell-surface expression and function. The clinical p.Lys23Glu mutation leads to an impairment in the interaction between Shugoshin-1 and HCN4, along with depressed funny-current and dysrhythmic activity in induced pluripotent stem cell derived cardiomyocytes derived from Chronic Atrial and Intestinal Dysrhythmia Syndrome patients. Our work reveals a critical non-canonical, cohesin-independent role for Shugoshin-1 in maintaining cardiac automaticity and identifies potential therapeutic avenues for cardiac pacemaking disorders, in particular Chronic Atrial and Intestinal Dysrhythmia Syndrome.

The zebrafish cohesin protein Sgo1 is required for cardiac function and eye development

“…The observed cardiac phenotype in sgo1 −/− larvae correlates well with the expression of sgo1 in the entire myocardium of the zebrafish heart with most abundant expression in the sinoatrial node, where the pacemaker cells reside 2 . Corroborating a role for Sgo1 in pacemaker cells is the recent observation that Sgo1 interacts with the potassium/sodium hyperpolarization‐activated cyclic nucleotide‐gated channel 4 (Hcn4) and is required for proper localization of the Hcn4 channel to the plasma membrane 13 . The Hcn4 channel is required for the so‐called funny current in pacemaker cells and mutations in HCN4 have been identified in patients with sick sinus syndrome and bradycardia 14‐17 .…”

“…2 Corroborating a role for Sgo1 in pacemaker cells is the recent observation that Sgo1 interacts with the potassium/sodium hyperpolarizationactivated cyclic nucleotide-gated channel 4 (Hcn4) and is required for proper localization of the Hcn4 channel to the plasma membrane. 13 The Hcn4 channel is required for the so-called funny current in pacemaker cells and mutations in HCN4 have been identified in patients with sick sinus syndrome and bradycardia. [14][15][16][17] Whether the observed reduction in contractility in sgo1 À/À larvae is also due to impaired Hcn4 activity is not clear and needs to be investigated further.…”

Developmental role of macrophages modelled in human pluripotent stem cell derived intestinal tissue

“…Human induced pluripotent stem cells (hiPSC) were generated at CR-CHUSJ Stem Cell core or in-house. The hiPSC lines SJi3252C2 and SJ3013C2 were derived from human fibroblasts using Cytotune 1.0 ™ (Invitrogen) and were previously characterized 58 . EU03.C2, and EU148.C5 were derived from human PBMC with Cytotune™ 2.0 (A16517, Invitrogen).…”

“…Human induced pluripotent stem cells (hiPSC) were generated at CR-CHUSJ Stem Cell core or in-house. The hiPSC lines SJi3252C2 and SJ3013C2 were derived from human fibroblasts using Cytotune 1.0 TM (Invitrogen) and were previously characterized 58 . Briefly, 85% confluent hiPSCs in a 6 well plate were passaged with EDTA and seeded 1/14-1/16 of a cell suspension per single well of 24 well plate.…”

The Caenorhabditis elegans Shugoshin regulates TAC-1 in cilia

“…In humans, a shorter splice variant of human Sgo1 , sSgo1 , localizes to the centrosome and is proposed to protect centriolar cohesion during mitosis 7 . Extranuclear functions of vertebrate SGO proteins are further supported by the recent discovery of its role in regulating pacemaker activity in the cell membranes of myocytes and its involvement in Chronic Atrial and Intestinal Dysrhythmia Syndrome (CAID) 8 . Consistent with post-mitotic functions for this protein family, mouse SGO1 is expressed in distinct terminally differentiated cells in neonatal mice, including neurons 9 , 10 .…”