Compartmentalized Accumulation of cAMP near Complexes of Multidrug Resistance Protein 4 (MRP4) and Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) Contributes to Drug-induced Diarrhea

Abstract

Background: Diarrhea is an adverse side effect associated with many therapeutics. Results: Irinotecan induced hyperactive cystic fibrosis transmembrane conductance regulator (CFTR) function by inhibiting multidrug resistance protein 4 (MRP4) and formation of MRP4-CFTR macromolecular complexes. Conclusion: MRP4-CFTR-containing macromolecular complexes play an important role in drug-induced diarrhea. Significance: These studies help define molecular mechanisms of drug-induced diarrhea.

Guanylate cyclase 2C agonism corrects CFTR mutants

“…This closed structure of an enterosphere encompassing a central lumen allows investigators to study fluid dynamics (i.e., secretion and absorption) caused by physiological alterations in the epithelia that can result in either swelling or shrinkage of the enterospheres (22). It turned out that enterospheres are extremely useful models to study CFTR function in which forskolin, a cAMP agonist, induces rapid swelling of the enteropsheres, with normal CFTR caused by fluid filling the central lumen as CFTR becomes active (23)(24)(25). Loss-of-function CFTR mutants fail to stimulate secretion in such an assay as demonstrated by us and others (23,24).…”

“…Preparation of mouse intestinal crypt and quantitation have been thoroughly described previously (25). Human crypts were isolated and cultured as reported earlier (40).…”

Chronic β2AR stimulation limits CFTR activation in human airway epithelia

“…PDEs are responsible for the breakdown of cAMP; in the airway epithelium, PDE-4 is the predominant isoform, allowing for precise control of cAMP levels at the local, perimembranous environment (34). Similarly, MRP4 has been demonstrated to function as a cAMP efflux pump in intestinal cells, regulating spatial cAMP concentration at the cell surface (46,47). Functional inhibition of both PDE-4 and MRP4, however, did not reverse albuterol-induced CFTR dysfunction (Supplemental Figure 1), making it unlikely that either of these regulators of spatial cAMP levels are implicit in our results.…”

Drug-induced secretory diarrhea: A role for CFTR

“…Crypts can be isolated and purified from the small intestine of adult mice or human biopsies and cultured in Matrigel [24]. Central lumen-like structures and protruding villus-like structures are formed in each enteroid, mimicking the native intestinal epithelium [25]. The interior walls of the enteroid consist of a polarized epithelial monolayer with a distinct inner luminal surface and an outer basolateral surface (Fig.…”