Akkermansia muciniphila secretome promotes α-synuclein aggregation in enteroendocrine cells.

The notion that the gut microbiota play a role in neurodevelopment, behavior and outcome of neurodegenerative disorders is recently taking place. A number of studies have consistently reported a greater abundance of Akkermansia muciniphila in Parkinsons disease (PD) fecal samples. Nevertheless, a functional link between A.muciniphila and sporadic PD remained unexplored. Here, we investigated whether A.muciniphila secretome could initiate the misfolding process of -synuclein (Syn) in enteroendocrine cells (EECs), which are part of the gut epithelium and possess many neuron-like properties. We found that A.muciniphila secretome is directly modulated by mucin, induces intracellular calcium (Ca2+) release, and causes increased mitochondrial Ca2+ uptake in EECs, which in turn leads to production of reactive oxygen species (ROS) and Syn aggregation. However, these events were efficiently inhibited once we buffered mitochondrial Ca2+. Thereby, these molecular insights provided here offer evidence that bacterial secretome is capable of inducing Syn aggregation in enteroendocrine cells. SYNOPSIS FIGURE DESCRIPTIONThe secretome isolated from the commensal gut bacterium Akkermansia muciniphila triggers intracellular Ca2+ signaling in enteroendocrine cells, leading to increased mitochondrial Ca2+ uptake. Mitochondrial Ca2+ overload leads to ROS generation culminating with Syn phosphorylation and aggregation (left panel). All these events were inhibited once mitochondrial Ca2+ is buffered (right panel). O_LIGram-negative gut bacterium Akkermansia muciniphila is consistently found more abundant in Parkinsons disease patients. C_LIO_LIAkkermansia muciniphila protein secretome composition is directly modulated by mucin and induces an IP3-independent endoplasmic reticulum (ER)-calcium release in enteroendocrine cells. C_LIO_LIThis Ca2+ release is triggered by direct activation of Ryanodine Receptors leading to increased mitochondrial Ca2+ uptake. C_LIO_LIMitochondrial Ca2+ overload leads to ROS generation culminating with Syn aggregation. C_LIO_LIBuffering mitochondrial Ca2+ efficiently inhibits A.muciniphila-induced Syn aggregation in enteroendocrine cells. C_LI