Monocytes and macrophages as biomarkers for the diagnosis of megalencephalic leukoencephalopathy with subcortical cysts

• Published in: Molecular and cellular neuroscience Vol. 56; pp. 307 - 321
• Main Authors: Petrini, Stefania, Minnone, Gaetana, Coccetti, Marianna, Frank, Claudio, Aiello, Chiara, Cutarelli, Alessandro, Ambrosini, Elena, Lanciotti, Angela, Brignone, Maria Stefania, D'Oria, Valentina, Strippoli, Raffaele, De Benedetti, Fabrizio, Bertini, Enrico, Bracci-Laudiero, Luisa
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.09.2013
• Subjects: Adolescent; Adult; Aquaporin-3; Biomarkers - metabolism; Calcium channel; Case-Control Studies; Cell Membrane - metabolism; Child; Cysts - diagnosis; Cysts - genetics; Cysts - metabolism; Endoplasmic Reticulum - metabolism; Hereditary Central Nervous System Demyelinating Diseases - diagnosis; Hereditary Central Nervous System Demyelinating Diseases - genetics; Hereditary Central Nervous System Demyelinating Diseases - metabolism; Humans; Ion homeostasis; Macrophages - metabolism; Megalencephalic leukoencephalopathy with subcortical cysts; Membrane Proteins - genetics; Membrane Proteins - metabolism; Middle Aged; MLC1; Monocytes - metabolism; Mutation; Protein Transport; Secretory Pathway; trans-Golgi Network - metabolism; Volume regulation; Volume regulation; MLC; Lamp2; MLC1; M/M; vSNAREvti1A; Ion homeostasis; AQP3; Megalencephalic leukoencephalopathy with subcortical cysts; Calcium channel; LPS; NaKβ1; Aquaporin-3; PDI; Stx17; Kir2.1; vesicular soluble N-ethylmaleimide-sensitive fusion protein-attachment protein receptor vti1A; protein disulphide-isomerase; lysosomal-associated membrane protein 2; Na,K-ATPase pump β1 subunit; monocyte-derived macrophages; syntaxin 17; Megalencephalic leukoencephalopathy with subcortical cysts protein-1; inwardly rectifying K+ channel 2.1; lipopolysaccharide
• ISSN: 1044-7431; 1095-9327
• DOI: 10.1016/j.mcn.2013.07.001

Megalencephalic leukoencephalopathy with subcortical cysts (MLC) is a rare congenital leukodystrophy characterized by macrocephaly, subcortical cysts and demyelination. The majority of patients harbor mutations in the MLC1 gene encoding for a membrane protein with largely unknown function. Mutations in MLC1 hamper its normal trafficking and distribution in cell membranes, leading to enhanced degradation. MLC1 protein is highly expressed in brain astrocytes and in circulating blood cells, particularly monocytes. We used these easily available cells and monocyte-derived macrophages from healthy donors and MLC1-mutated patients to study MLC1 expression and localization, and to investigate how defective MLC1 mutations may affect macrophage functions. RT-PCR, western blot and immunofluorescence analyses show that MLC1 is expressed in both monocytes and macrophages, and its biosynthesis follows protein trafficking between endoplasmic reticulum and trans-Golgi network and the secretory pathway to the cell surface. MLC1 is transported along the endosomal recycling pathway passing through Rab5+ and Rab11A+vesicles before lysosomal degradation. Alterations in MLC1 trafficking and distribution were observed in macrophages from MLC1-mutated patients, which also showed changes in the expression and localization of several proteins involved in plasma membrane permeability, ion and water homeostasis and ion-regulated exocytosis. As a consequence of these alterations, patient-derived macrophages show abnormal cell morphology and intracellular calcium influx and altered response to hypo-osmotic stress. Our results suggest that blood-derived macrophages may give relevant information on MLC1 function and may be considered as valid biomarkers for MLC diagnosis and for investigating therapeutic strategies aimed to restore MLC1 trafficking in patient cells.