S100A10 and major depressive disorder: Extensive studies on the function of p11 revealed that p11 potentiates serotonin neurotransmission via multiple mechanisms including recruitment of 5-HT1B and 5-HT4 receptors at the cell surface (Svenningsson et al., 2006; Warner-Schmidt et al., 2009), and regulates depression-like behaviors and responses to antidepressants (Svenningsson et al., 2013; Medrihan et al., 2017).