O -Linked β- N -Acetylglucosamine Transferase Directs Cell Proliferation in Idiopathic Pulmonary Arterial Hypertension

Abstract

Background Idiopathic Pulmonary arterial Hypertension (IPAH) is a cardiopulmonary disease characterized by cellular proliferation and vascular remodeling. A more recently recognized characteristic of the disease is dysregulation of glucose metabolism. The primary link between altered glucose metabolism and cell proliferation in IPAH has not been elucidated. We aimed to determine the relationship between glucose metabolism and smooth muscle cell proliferation in IPAH. Methods and Results Human IPAH and control patient lung tissues and pulmonary artery smooth muscle cells (PASMCs) were used to analyze a specific pathway of glucose metabolism, the hexosamine biosynthetic pathway (HBP). We measured the levels of O-linked N-acetylglucosamine modification (O-GlcNAc), O-GlcNAc transferase (OGT), and O-GlcNAc hydrolase (OGA) in control and IPAH cells and tissues. Our data suggests that the activation of the HBP directly increased OGT levels and activity triggering changes in glycosylation and PASMC proliferation. Partial knockdown of OGT in IPAH PASMCs resulted in reduced global O-GlcNAc levels and abrogated PASMC proliferation. The increased proliferation observed in IPAH PASMCs was directly impacted by proteolytic activation of the cell cycle regulator, host cell factor-1 (HCF-1). Conclusions Our data demonstrate that HBP flux is increased in IPAH and drives OGT-facilitated PASMC proliferation through specific proteolysis and direct activation of HCF-1. These findings establish a novel regulatory role for OGT in IPAH, shed a new light on our understanding of the disease pathobiology, and provide opportunities to design novel therapeutic strategies for IPAH.

MicroRNA-424 Predicts a Role for β-1,4 Branched Glycosylation in Cell Cycle Progression

“…Previous analysis of the 3Ј-UTR of OGT revealed that it is one of the most highly regulated glycogenes (41). O-GlcNAc, the epitope controlled by this enzyme, is involved in cell proliferation (42,43), consistent with targeting by miR-424. Thus, further exploration of the interaction between miR-424 and OGT in alternate biological systems is warranted.…”

Bone Morphogenic Protein Type 2 Receptor Mutation-Independent Mechanisms of Disrupted Bone Morphogenetic Protein Signaling in Idiopathic Pulmonary Arterial Hypertension

“…Collectively, this report suggests that altered BMP signaling in IPAH can result independent of BMPR2 mutation status. We put forth the notion that Smurf-1 expression is stimulated by glucose, which has been confirmed to be dysregulated in the lungs of patients with IPAH (35)(36)(37)(38)(39), and may trigger the degradation of BMP-regulated Smads and reduction in Smad activation. The role of glucose in the regulation of Gremlin-1 expression in IPAH is also discussed.…”

“…PASMCs were used between passages 5 and 9 and were grown in low glucose (1 g/L) SMBM-2 media (Lonza, Walkersville, MD) supplemented with growth factors (Growth Factor Bullet Kit; Lonza) unless otherwise specified for experimental conditions as described (38).…”

“…Lung tissue and PASMCs were prepared as described previously (38) with the addition of phosphatase inhibitors (Sigma-Aldrich) and were subjected to SDS-PAGE and Western blot analysis. Nitrocellulose membranes were probed with antisera for the following: Cruz) and b-Actin (1/10,000; Santa Cruz) were blocked, washed, and imaged using an Odyssey Infrared Imaging System (Li-Cor Biosciences, Lincoln, NE).…”

Profiling the Role of Mammalian Target of Rapamycin in the Vascular Smooth Muscle Metabolome in Pulmonary Arterial Hypertension

“…Dysregulated glycosylation, caused mostly by failure of distinct steps in glycan formation, leads to severe morphogenic and metabolic disorders and is linked to a number of genetic diseases and cancer, 23,24 and a recent study from the Dweik group provides a strong mechanistic link between dysregulated glycosylation and PAVSMC proliferation in PAH. 25 Such a broadly shared deficit of sugars, amino sugars, and nucleotide sugars in the PAH cohort and its high dependence on mTOR activity strongly suggest that PAVSMCs in PAH have mTOR-dependent alterations of protein and lipid glycosylation that may dramatically affect multiple signaling pathways involved in disease pathogenesis.…”