PDE3A functionally and physically interacts with CFTR. Inhibition of PDE3A generates compartmentalized cAMP, which further clusters PDE3A and CFTR into microdomains at the plasma membrane of epithelial cells and potentiates CFTR channel function. Our findings provide insights into the important role of PDE3A in compartmentalized cAMP signaling.

Cystic fibrosis (CF) is a genetic disorder caused by defective CF Transmembrane Conductance Regulator (CFTR) function. Insulin producing pancreatic islets are located in close proximity to the pancreatic duct and there is a possibility of impaired cell-cell signaling between pancreatic ductal epithelial cells (PDECs) and islet cells as causative in CF. To study this possibility, we present an in vitro co-culturing system, pancreas-on-a-chip. Furthermore, we present an efficient method to micro dissect patient-derived human pancreatic ducts from pancreatic remnant cell pellets, followed by the isolation of PDECs. Here we show that defective CFTR function in PDECs directly reduced insulin secretion in islet cells significantly. This uniquely developed pancreatic function monitoring tool will help to study CF-related disorders in vitro, as a system to monitor cell-cell functional interaction of PDECs and pancreatic islets, characterize appropriate therapeutic measures and further our understanding of pancreatic function.

Background: MRP4 is an endogenous transporter of cyclic nucleotides that can regulate cell migration. The role of MRP4 in fibroblast migration is unknown. Results: MRP4-deficient fibroblasts migrate faster and have a moderately higher level of intracellular cyclic nucleotides. Conclusion: Inhibition of MRP4 increases fibroblast migration via alteration of intracellular cyclic nucleotide levels. Significance: Inhibition of MRP4 facilitates wound repair.

Cystic fibrosis (CF) is a recessive genetic disease caused by mutations in CFTR, a plasma-membrane-localized anion channel. The most common mutation in CFTR, deletion of phenylalanine at residue 508 (ΔF508), causes misfolding of CFTR resulting in little or no protein at the plasma membrane. The CFTR corrector VX-809 shows promise for treating CF patients homozygous for ΔF508. Here, we demonstrate the significance of protein–protein interactions in enhancing the stability of the ΔF508 CFTR mutant channel protein at the plasma membrane. We determined that VX-809 prolongs the stability of ΔF508 CFTR at the plasma membrane. Using competition-based assays, we demonstrated that ΔF508 CFTR interacts poorly with Na+/H+ exchanger regulatory factor 1 (NHERF1) compared to wild-type CFTR, and VX-809 significantly increased this binding affinity. We conclude that stabilized CFTR–NHERF1 interaction is a determinant of the functional efficiency of rescued ΔF508 CFTR. Our results demonstrate the importance of macromolecular-complex formation in stabilizing rescued mutant CFTR at the plasma membrane and suggest this to be foundational for the development of a new generation of effective CFTR-corrector-based therapeutics.

Platelet activation initiates an upsurge in 18:2 and 20:4 lysophosphatidic acid (LPA) production. The biochemical pathway responsible for LPA production during blood clotting is not fully understood. We have purified a phospholipase A1 (PLA1) from thrombin‐activated human platelets using sequential chromatographic steps followed by fluorophosphonate‐biotin affinity labeling and proteomics. We identified acyl‐protein thioesterase 1 (aka. lysophospholipase A1, accession code ) as a novel PLA1. Addition of this recombinant PLA1 significantly increased the production of sn‐2‐esterified polyunsaturated LPCs and the corresponding LPAs in plasma. We next examined the regioisomeric preference of lysophospholipase D/autotaxin (ATX), which is the subsequent step in LPA production. To prevent acyl‐migration regioisomers of oleyl‐sn‐glycero‐3‐phosphocholine (LPAF) were synthesized. ATX preferred the sn‐1 over the sn‐2 regioisomer of LPAF. We propose the following LPA production pathway in blood: 1) Activated platelet secrete PLA1. 2) PLA1 generates a pool of sn‐2 lysophospholipids. 3) These newly generated sn‐2 lysophospholipids undergo acyl migration to yield sn‐1 lysophospholipids, which are the preferred substrates of ATX. 4) ATX cleaves the sn‐1 lysophospholipids to generate sn‐1 LPA species predominant with 18:2 and 20:4 fatty acids.

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.

Preciseness of cellular behavior depends upon how an extracellular cue mobilizes a correct orchestra of cellular messengers and effector proteins spatially and temporally. This concept, termed compartmentalization of cellular signaling, is now known to form the molecular basis of many aspects of cellular behavior in health and disease. The cyclic nucleotides cAMP and cGMP are ubiquitous cellular messengers that can be compartmentalized in three ways: first, by their physical containment; second, by formation of multiple protein signaling complexes; and third, by their selective depletion. Compartmentalized cyclic nucleotide signaling is a very prevalent response among all cell types. In order to understand how it becomes relevant to cellular behavior, it is important to know how it is executed in cells to regulate physiological responses and, also, how its execution or dysregulation can lead to a pathophysiological condition, which forms the current scope of the presented review.

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