Inositol 1,4,5-triphosphate receptor-associated cGMP kinase substrate 1 (IRAG1) is a substrate protein of the NO/cGMP-signaling pathway and forms a ternary complex with the cGMP-dependent protein kinase I beta (PKGI beta) and the inositol triphosphate receptor I (IP3R-I). Functional studies about IRAG1 exhibited that IRAG1 is specifically phosphorylated by the PKGI beta, regulating cGMP-mediated IP3-dependent Ca2+-release. IRAG1 is widely distributed in murine tissues, e.g., in large amounts in smooth muscle-containing tissues and platelets, but also in lower amounts, e.g., in the spleen. The NO/cGMP/PKGI signaling pathway is important in several organ systems. A loss of PKGI causes gastrointestinal disorders, anemia and splenomegaly. Due to the similar tissue distribution of the PKGI beta to IRAG1, we investigated the pathophysiological functions of IRAG1 in this context. Global IRAG1-KO mice developed gastrointestinal bleeding, anemia-associated splenomegaly and iron deficiency. Additionally, Irag1-deficiency altered the protein levels of some cGMP/PKGI signaling proteins-particularly a strong decrease in the PKGI beta-in the colon, spleen and stomach but did not change mRNA-expression of the corresponding genes. The present work showed that a loss of IRAG1 and the PKGI beta/IRAG1 signaling has a crucial function in the development of gastrointestinal disorders and anemia-associated splenomegaly. Furthermore, global Iragl-deficient mice are possible in vivo model to investigate PKGI beta protein functions.