Megalencephalic leukoencephalopathy with subcortical cysts protein-1 (MLC1) is a
membrane protein expressed by perivascular astrocytes. MLC1 mutations cause MLC, an incurable leukodystrophy characterized by
macrocephaly,
brain edema,
cysts, myelin vacuolation, and
astrocytosis, leading to cognitive/motor impairment and
epilepsy. Although its function is unknown, MLC1 favors regulatory volume decrease after astrocyte osmotic swelling and down-regulates intracellular signaling pathways controlling astrocyte activation and proliferation. By combining analysis of human brain tissues with in vitro experiments, here we investigated MLC1 role in astrocyte activation during
neuroinflammation, a pathological condition exacerbating patient symptoms. MLC1 upregulation was observed in brain tissues from
multiple sclerosis, Alzheimer's, and Creutzfeld-Jacob disease, all pathologies characterized by strong
astrocytosis and release of inflammatory
cytokines, particularly IL-1β. Using
astrocytoma lines overexpressing wild-type (WT) or mutated MLC1 and astrocytes from control and Mlc1 knock-out (KO) mice, we found that IL-1β stimulated WT-MLC1 plasma membrane expression in
astrocytoma cells and control primary astrocytes. In
astrocytoma, WT-MLC1 inhibited the activation of IL-1β-induced inflammatory signals (pERK, pNF-kB) that, conversely, were constitutively activated in mutant expressing cells or abnormally upregulated in KO astrocytes. WT-MLC1+ cells also expressed reduced levels of the
astrogliosis marker pSTAT3. We then monitored MLC1 expression timing in a demyelinating/remyelinating murine cerebellar organotypic culture model where, after the
demyelination and release of inflammatory
cytokines, recovery processes occur, revealing MLC1 upregulation in these latter phases. Altogether, these findings suggest that by modulating specific pathways, MLC1 contributes to restore astrocyte homeostasis after
inflammation, providing the opportunity to identify
drug target molecules to slow down
disease progression.