Astrocytic activation of EMMPRIN contributes to their pathological phenotype in ALS

Amyotrophic Lateral Sclerosis (ALS) is a fatal disease characterised by the degeneration of upper and lower motoneurons. Onset and progression of the disease are determined by both cell-autonomous neuronal dysfunctions and non-cell-autonomous factors, mainly due to activation of glial cells such as astrocytes and microglia.

The Extracellular Matrix Metalloproteinases INducer (EMMPRIN), a glycoprotein expressed by various cell types including neurons, is the major activator of matrix metalloproteinases (MMPs) synthesis and release. EMMPRIN activation can be induced by peptidyl-prolyl isomerase A (PPIA), a chaperone protein with cis/trans isomerase activity, that exhibits cytokine- and chemokine-like behaviour. Previous studies showed that PPIA is highly released in the cerebrospinal fluid (CSF) of ALS patients and animal models where, by activating EMMPRIN on motoneurons, induces neuronal death.

Here, we show that EMMPRIN is expressed also by astrocytes, suggesting this cell type as sensitive as motoneurons to PPIA-mediated EMMPRIN activation. We observed that that PPIA-mediated EMMPRIN activation prompt astrocytes toward a pro-inflammatory profile. Interestingly, we found that this pathogenic profile can be reverted by an anti-EMMPRIN antibody. Finally, we provide evidence that the activation of EMMPRIN is relevant for mutant SOD1 and TDP-43 conditions.

In conclusion, we demonstrate that EMMPRIN activation in ALS occurs also in astrocytes where it exacerbates their pathological phenotype possibly contributing to the progression of the disease. Furthermore, we suggest the potential use of an anti-EMMPRIN antibody to reduce astrocytic activation during the disease.