Pompe Disease Results in a Golgi-based Glycosylation Deficit in Human Induced Pluripotent Stem Cell-derived Cardiomyocytes

• Published in: The Journal of biological chemistry 2015-01, Vol.290 (5), p.3121-3136
• Main Authors: Raval, Kunil K., Tao, Ran, White, Brent E., De Lange, Willem J., Koonce, Chad H., Yu, Junying, Kishnani, Priya S., Thomson, James A., Mosher, Deane F., Ralphe, John C., Kamp, Timothy J.
• Format: Article
• Language: English
• Subjects: Autophagy; Blotting, Western; Cardiomyopathy; Cells, Cultured; Genotype; Glycogen Storage Disease Type II - metabolism; Glycogen Storage Disease Type II - pathology; Glycosylation; Golgi; Golgi Apparatus - metabolism; Humans; Immunohistochemistry; Induced Pluripotent Stem Cell (iPSC); Induced Pluripotent Stem Cells - cytology; Lysosomal Glycoprotein; Molecular Bases of Disease; Myocytes, Cardiac - pathology; N-linked Glycosylation; Pompe Disease; Tissue Engineering
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M114.628628

Infantile-onset Pompe disease is an autosomal recessive disorder caused by the complete loss of lysosomal glycogen-hydrolyzing enzyme acid α-glucosidase (GAA) activity, which results in lysosomal glycogen accumulation and prominent cardiac and skeletal muscle pathology. The mechanism by which loss of GAA activity causes cardiomyopathy is poorly understood. We reprogrammed fibroblasts from patients with infantile-onset Pompe disease to generate induced pluripotent stem (iPS) cells that were differentiated to cardiomyocytes (iPSC-CM). Pompe iPSC-CMs had undetectable GAA activity and pathognomonic glycogen-filled lysosomes. Nonetheless, Pompe and control iPSC-CMs exhibited comparable contractile properties in engineered cardiac tissue. Impaired autophagy has been implicated in Pompe skeletal muscle; however, control and Pompe iPSC-CMs had comparable clearance rates of LC3-II-detected autophagosomes. Unexpectedly, the lysosome-associated membrane proteins, LAMP1 and LAMP2, from Pompe iPSC-CMs demonstrated higher electrophoretic mobility compared with control iPSC-CMs. Brefeldin A induced disruption of the Golgi in control iPSC-CMs reproduced the higher mobility forms of the LAMPs, suggesting that Pompe iPSC-CMs produce LAMPs lacking appropriate glycosylation. Isoelectric focusing studies revealed that LAMP2 has a more alkaline pI in Pompe compared with control iPSC-CMs due largely to hyposialylation. MALDI-TOF-MS analysis of N-linked glycans demonstrated reduced diversity of multiantennary structures and the major presence of a trimannose complex glycan precursor in Pompe iPSC-CMs. These data suggest that Pompe cardiomyopathy has a glycan processing abnormality and thus shares features with hypertrophic cardiomyopathies observed in the congenital disorders of glycosylation. Background: How the absence of lysosomal enzyme acid α-glucosidase causes hypertrophic cardiomyopathy in Pompe disease is unknown. Results: Pompe patient-induced pluripotent stem cell-derived cardiomyocytes have normal autophagic and contractile function but exhibit a deficit of Golgi-based protein glycosylation. Conclusion: Loss of the lysosomal glycogen hydrolyzing ability results in protein glycosylation deficits. Significance: Malfunctioning proteins due to misglycosylation may contribute to the pathophysiology of Pompe cardiomyopathy.