TcCARP3 modulates compartmentalized cAMP signals involved in osmoregulation, infection of mammalian cells, and colonization of the triatomine vector in the human pathogen <i>Trypanosoma cruzi</i>

<i>Trypanosoma cruzi</i> is the causative agent of Chagas disease, a zoonotic infectious disease considered a leading cause of cardiomyopathy, disability, and premature death in the Americas. This parasite spends its life between a mammalian host and an arthropod vector, undergoing essential transitions among different developmental forms. How <i>T. cruzi</i> senses microenvironmental changes that trigger cellular responses necessary for parasite survival has remained largely unknown. Cyclic AMP (cAMP) is a universal second messenger that has been shown to regulate key cellular processes in trypanosomes, in which cAMP response proteins (CARPs) have been proposed to be modulators or effectors of a PKA-independent signaling pathway. In this study, we aimed to investigate the role of TcCARP3 in cAMP signaling throughout the <i>T. cruzi</i> life cycle. Our results show that TcCARP3 shares a dual localization (flagellar tip and contractile vacuole complex) with adenylate cyclase 1 (TcAC1) in the main developmental stages of the parasite. We also found that TcCARP3 directly interacts with several TcACs, modulating the intracellular content of cAMP. Through generation of <i>TcCARP3</i> knockout, addback, and overexpression cell lines, we showed that modulation of gene expression affects the parasite's ability to differentiate, respond to osmotic stress, invade mammalian cells and replicate within them, and colonize the hindgut of the triatomine vector. In addition, we identified several signaling proteins interacting with TcCARP3 in what we propose are cAMP signaling microdomains. Our results unveil a key role for TcCARP3 as a modulator of cAMP signals necessary for parasite differentiation and survival throughout the <i>T. cruzi</i> life cycle.IMPORTANCECyclic AMP (cAMP) signaling pathways are poorly understood in the stercorarian parasite <i>Trypanosoma cruzi</i>. Specifically, the mechanisms driving the activation of TcACs in response to microenvironmental stress are completely unknown. This study unveils the role of TcCARP3 in modulating the content of cAMP through the interaction with several TcACs and putative cAMP effectors in <i>T. cruzi</i>. Particularly, TcCARP3 interacts with TcAC1 in the main developmental stages of this parasite's life cycle, where both proteins display a dual localization pattern. These results provide new evidence supporting the compartmentalization of cAMP signals in trypanosomes. Moreover, our data unequivocally demonstrates that TcCARP3 is required for essential cellular processes, such as response to osmotic stress, host cell invasion, intracellular replication, and the ability to colonize the hindgut of the triatomine vector. In summary, we found that TcCARP3 is an adenylate cyclase interactor that modulates cAMP signals necessary for the life cycle progression of <i>T. cruzi</i>.