Biology subjects

Heo, Y.

Publications and source records attributed to Heo, Y..

4 recordsLinked to original sources

bioRxiv2022

Atomistic structure of the interlocking claw-like amyloid fibril of full-length glucagon

Glucagon is a peptide hormone which posits a significant potential as a therapeutic molecule for various human diseases. One of the major challenges hampering medicinal application of glucagon, however, is its insoluble and aggregation-prone property. Although glucagon is dissolvable, it aggregates easily and forms amyloid fibrils. To date, despite many studies to understand how glucagon aggregates and fibrillizes, its detailed amyloidogenesis mechanism is still elusive, particularly due to insufficient structural information of glucagon amyloid fibrils. Here we report the novel structure of a glucagon amyloid fibril, which was determined with cryo-electron microscopy (cryo-EM) to a 3.8-[A] resolution. Our model features with tight and extensive inter-monomer interactions, which efficiently stabilize the entire chain of full-length glucagon into the V-shape conformation, clamping the other monomer to construct a dimeric architecture orthogonal to the fibril axis. Notably, the current structure significantly differs from the previous solid-state NMR model, which gives direct evidence for multiple and dynamic amyloidogenesis mechanisms of glucagon. In addition, our results are expected to provide important insights to appreciate the molecular details of glucagon in its initial amyloidogenesis and fibril elongation processes.

molecular biology↗

bioRxiv2022

Survivin is a mechanosensitive cell cycle regulator in vascular smooth muscle cells

Stiffened arteries are a pathology of atherosclerosis, hypertension, and coronary artery disease and a key risk factor for cardiovascular disease events. The increased stiffness of arteries triggers the hypermigration and hyperproliferation of vascular smooth muscle cells (VSMCs), leading to neointimal hyperplasia and accelerated neointima formation, but the mechanism of this trigger is not known. Our analyses of whole-transcriptome microarray data sets from mouse VSMCs cultured on stiff hydrogels simulating arterial pathology and from injured mouse femoral arteries revealed 80 genes that were differentially regulated (74 upregulated and 6 downregulated) relative to expression in control VSMCs cultured on soft hydrogels and in uninjured femoral arteries. A functional enrichment analysis revealed that these stiffness-sensitive genes are linked to cell cycle progression and proliferation. Furthermore, we found that survivin, a member of the inhibitor of apoptosis protein family, mediates stiffness-sensitive cell cycling and proliferation in vivo and in vitro as determined by gene network and pathway analyses, RT-qPCR, and immunoblotting. The stiffness signal is mechanotransduced via FAK and Rac signaling to regulate survivin expression, establishing a regulatory pathway for how the stiffness of the cellular microenvironment affects VSMC behaviors. Our findings indicate that survivin is necessary for VSMC cycling and proliferation and regulates stiffness-responsive phenotypes.

cell biology↗

bioRxiv2022

Survivin Regulates Intracellular Stiffness and Extracellular Matrix Production in Vascular Smooth Muscle Cells

Vascular dysfunction is a common cause of cardiovascular diseases characterized by the narrowing and stiffening of arteries, such as atherosclerosis, restenosis, and hypertension. Arterial narrowing results from the aberrant proliferation of vascular smooth muscle cells (VSMCs) and their increased synthesis and deposition of extracellular matrix (ECM) proteins. These, in turn, are modulated by arterial stiffness, but the mechanism for this is not fully understood. We found that survivin (an inhibitor of apoptosis) is an important regulator of stiffness-mediated ECM synthesis and intracellular stiffness in VSMCs. Whole-transcriptome analysis and cell culture experiments showed that survivin expression is upregulated in injured femoral arteries in mice and in human VSMCs cultured on stiff fibronectin-coated hydrogels. Suppressed expression of survivin in human VSMCs and mouse embryonic fibroblasts decreased the stiffness-mediated expression of ECM components implicated in arterial stiffness, namely, collagen-I, fibronectin, and lysyl oxidase. By contrast, expression of these proteins was upregulated by the overexpression of survivin in human VSMCs cultured on soft hydrogels. Atomic force microscopy analysis showed that suppressed or enhanced expression of survivin decreases or increases intracellular stiffness, respectively. These findings suggest a novel mechanism by which survivin modulates arterial stiffness.

cell biology↗

bioRxiv2022

Cryo-EM structure of human somatostatin receptor 2 complex with its agonist somatostatin delineates the ligand binding specificity

Somatostatin is a peptide hormone regulating endocrine systems through binding to G-protein-coupled somatostatin receptors. somatostatin receptor 2 (SSTR2) is one of the human somatostatin receptors and highly implicated in cancers and neurological disorders. Here, we report the high resolution cryo-EM structure of full-length human SSTR2 bound to the agonist somatostatin (SST-14) complex with inhibitory G (Gi) proteins. Our structure shows that seven transmembrane helices form a deep pocket for ligand binding and that the highly conserved Trp-Lys motif of SST-14 positions at the bottom of the pocket. Furthermore, our sequence analysis combined with AlphaFold modeled structures of other SSTR isoforms provide how SSTR family proteins specifically interact with their cognate ligands. This work provides the first glimpse into the molecular recognition of somatostatin receptor and crucial resource to develop therapeutics targeting somatostatin receptors.

biophysics↗