Risperidone is a second-generation antipsychotic that causes weight gain. We hypothesized that risperidone-induced shifts in the gut microbiome are mechanistically involved in its metabolic consequences. Wild-type female C57BL/6J mice treated with risperidone (80 μg/day) exhibited significant excess weight gain, due to reduced energy expenditure, which correlated with an altered gut microbiome. Fecal transplant from risperidone-treated mice caused a 16% reduction in total resting metabolic rate in naïve recipients, attributable to suppression of non-aerobic metabolism. Risperidone inhibited growth of cultured fecal bacteria grown anaerobically more than those grown aerobically. Finally, transplant of the fecal phage fraction from risperidone-treated mice was sufficient to cause excess weight gain in naïve recipients, again through reduced energy expenditure. Collectively, these data highlight a major role for the gut microbiome in weight gain following chronic use of risperidone, and specifically implicates the modulation of non-aerobic resting metabolism in this mechanism.

Extracytoplasmic function (ECF) σ factors are a diverse family of alternative σ factors that allow bacteria to sense and respond to changes in the environment. σ is an ECF σ factor found primarily in low-GC Gram-positive bacteria and is required for lysozyme resistance in several opportunistic pathogens. In the absence of lysozyme, σ is inhibited by the anti-σ factor RsiV. In response to lysozyme, RsiV is degraded via the process of regulated intramembrane proteolysis (RIP). RIP is initiated by cleavage of RsiV at site 1, which allows the intramembrane protease RasP to cleave RsiV within the transmembrane domain at site 2 and leads to activation of σ Previous work suggested that RsiV is cleaved by signal peptidase at site 1. Here we demonstrate that signal peptidase is sufficient for cleavage of RsiV only in the presence of lysozyme and provide evidence that multiple signal peptidases can cleave RsiV This cleavage is dependent upon the concentration of lysozyme, consistent with previous work that showed that binding to RsiV was required for σ activation. We also show that signal peptidase activity is required for site 1 cleavage of RsiV Thus, we demonstrate that signal peptidase is the site 1 protease for RsiV. Extracytoplasmic function (ECF) σ factors are a diverse family of alternative σ factors that respond to extracellular signals. The ECF σ factor σ is present in many low-GC Gram-positive bacteria and induces resistance to lysozyme, a component of the innate immune system. The anti-σ factor RsiV inhibits σ activity in the absence of lysozyme. Lysozyme binds RsiV, which initiates a proteolytic cascade leading to destruction of RsiV and activation of σ This proteolytic cascade is initiated by signal peptidase, a component of the general secretory system. We show that signal peptidase is necessary and sufficient for cleavage of RsiV at site 1 in the presence of lysozyme. This report describes a role for signal peptidase in controlling gene expression.

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Golgi and ER export signals have widely been used to improve membrane trafficking of optical bio-sensors. Previously, we reported a linker modified version of a genetically encoded voltage indicator engineered to image action potential spikes of neurons. Optimization of membrane expression was expected to improve the signal to noise ratio by minimizing unwanted none voltage dependent fluorescence. Accordingly, either Golgi or ER trafficking motif, or both were introduced into Bongwoori-R3 and affected its voltage sensing properties such as the kinetics, responsive voltage range and DF/F signal size. The ER motif improved the fluorescence response but it also caused increased time constants and a shifted V 1/2 toward hyperpolarization. Introducing spacers between the fluorescent protein and the ER targeting motif recovered the response speed while maintaining the improved fluorescence signal size.

I have learned so much throughout my graduate career. Thank you to my fellow graduate students, lab mates, family and friends. First, thank you to my advisor Craig Ellermeier. You have provided me with support, advice, encouragement to become an independent scientist and gave me the freedom to pursue interesting projects. Also, thank you for not getting mad every time I decorated your office with Iowa Hawkeye décor. To my thesis committee, Tim and David, thank you for your continued encouragement and contribution. To the Ellermeier lab, thank you for your unwavering support. I looked forward to going to lab every day and you made it easy for me to learn and grow. T, thank you for always being available to chat and grab sweet potato fries. Lincoln, Ute, Kelsie and Gabriela, thank you for the conversations that ranged from science, cycling, climbing and sports. To the crystallography core, thank you Sankar and Lokesh for teaching me about protein work and allowing me to ask many questions. To the graduate students, thank you for making my transition into the Microbiology program an easy one. To Kayley, thank you for always having a listening ear and for helping me train for my first 5K. Thank you to everyone in the Microbiology office for your willingness to help. Finally, I would like to thank my family. To my parents Delia and Benigno, my sister Digna, brothers Eduardo and Nino, my many nieces and nephews, and to my fiancé for always encouraging me, even when they had no idea what I was working on.