Gene therapy with phosphodiesterases 2A and 4B ameliorates heart failure and arrhythmias by improving subcellular cAMP compartmentation.

Aims: Gene therapy with cardiac phosphodiesterases (PDEs), such as phosphodiesterase 4B (PDE4B), has recently been described to effectively prevent heart failure (HF) in mice. However, exact molecular mechanisms of its beneficial effects, apart from general lowering of cardiomyocyte cyclic adenosine monophosphate (cAMP) levels, have not been elucidated. Here, we studied whether gene therapy with two types of PDEs, namely PDE2A and PDE4B, can prevent pressure-overload-induced HF in mice by acting on and restoring altered cAMP compartmentation in distinct subcellular microdomains.

Lysosomal lipid switch sensitises to nutrient deprivation and mTOR targeting in pancreatic cancer.

Objective: Pancreatic ductal adenocarcinoma (PDAC) is an aggressive disease with limited therapeutic options. However, metabolic adaptation to the harsh PDAC environment can expose liabilities useful for therapy. Targeting the key metabolic regulator mechanistic target of rapamycin complex 1 (mTORC1) and its downstream pathway shows efficacy only in subsets of patients but gene modifiers maximising response remain to be identified.

PI3K Signaling in Mechanisms and Treatments of Pulmonary Fibrosis Following Sepsis and Acute Lung Injury.

Pulmonary fibrosis is a pathological fibrotic process affecting the lungs of five million people worldwide. The incidence rate will increase even more in the next years due to the long-COVID-19 syndrome, but a resolving treatment is not available yet and usually prognosis is poor. The emerging role of the phosphatidylinositol 3-kinase (PI3K)/AKT signaling in fibrotic processes has inspired the testing of drugs targeting the PI3K/Akt pathway that are currently under clinical evaluation.

Phosphoinositide Conversion Inactivates R-RAS and Drives Metastases in Breast Cancer.

Breast cancer is the most prevalent cancer and a major cause of death in women worldwide. Although early diagnosis and therapeutic intervention significantly improve patient survival rate, metastasis still accounts for most deaths. Here it is reported that, in a cohort of more than 2000 patients with breast cancer, overexpression of PI3KC2α occurs in 52% of cases and correlates with high tumor grade as well as increased probability of distant metastatic events, irrespective of the subtype.

PI(3,4)P2-mediated cytokinetic abscission prevents early senescence and cataract formation.

Cytokinetic membrane abscission is a spatially and temporally regulated process that requires ESCRT (endosomal sorting complexes required for transport)–dependent control of membrane remodeling at the midbody, a subcellular organelle that defines the cleavage site. Alteration of ESCRT function can lead to cataract, but the underlying mechanism and its relation to cytokinesis are unclear. We found a lens-specific cytokinetic process that required PI3K-C2α (phosphatidylinositol-4-phosphate 3-kinase catalytic subunit type 2α), its lipid product PI(3,4)P (phosphatidylinositol 3,4-bisphosphate), and the PI(3,4)P–binding ESCRT-II subunit VPS36 (vacuolar protein-sorting-associated protein 36).

A Novel Multiplex qRT-PCR Assay to Detect SARS-CoV-2 Infection: High Sensitivity and Increased Testing Capacity.

Rapid and sensitive screening of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is essential to limit the spread of the global pandemic we are facing. Quantitative real-time reverse transcription-polymerase chain reaction (qRT-PCR) is currently used for the clinical diagnosis of SARS-CoV-2 infection using nasopharyngeal swabs, tracheal aspirates, or bronchoalveolar lavage (BAL) samples. Despite the high sensitivity of the qRT-PCR method, false negative outcomes might occur, especially in patients with a low viral load.

Cardiac Overexpression of PDE4B Blunts β-Adrenergic Response and Maladaptive Remodeling in Heart Failure.

Background: The cyclic AMP (adenosine monophosphate; cAMP)-hydrolyzing protein PDE4B (phosphodiesterase 4B) is a key negative regulator of cardiac β-adrenergic receptor stimulation. PDE4B deficiency leads to abnormal Ca handling and PDE4B is decreased in pressure overload hypertrophy, suggesting that increasing PDE4B in the heart is beneficial in heart failure.

Methods: We measured PDE4B expression in human cardiac tissues and developed 2 transgenic mouse lines with cardiomyocyte-specific overexpression of PDE4B and an adeno-associated virus serotype 9 encoding PDE4B.

The PI3K/Akt/mTOR pathway in polycystic kidney disease: A complex interaction with polycystins and primary cilium.

Over-activation of the PI3K/Akt/mTOR network is a well-known pathogenic event that leads to hyper-proliferation. Pharmacological targeting of this pathway has been developed for the treatment of multiple diseases, including cancer. In polycystic kidney disease (PKD), the mTOR cascade promotes cyst growth by boosting proliferation, size and metabolism of kidney tubule epithelial cells.

Class II PI3Ks at the Intersection between Signal Transduction and Membrane Trafficking.

Phosphorylation of inositol phospholipids by the family of phosphoinositide 3-kinases (PI3Ks) is crucial in controlling membrane lipid composition and regulating a wide range of intracellular processes, which include signal transduction and vesicular trafficking. In spite of the extensive knowledge on class I PI3Ks, recent advances in the study of the three class II PI3Ks (PIK3C2A, PIK3C2B and PIK3C2G) reveal their distinct and non-overlapping cellular roles and localizations. By finely tuning membrane lipid composition in time and space among different cellular compartments, this class of enzymes controls many cellular processes, such as proliferation, survival and migration.

Class II PI3K Functions in Cell Biology and Disease.

The phosphoinositide 3-kinases (PI3Ks) are a family of lipid kinases that phosphorylate inositol phospholipids, thereby controlling membrane lipid composition and regulating a wide range of intracellular processes, including vesicular trafficking and signal transduction. Despite the vast knowledge on class I PI3Ks, recent studies are only now revealing the importance of class II PI3Ks in cell proliferation, survival, and migration. Increasing evidence suggests that the three class II PI3Ks isoforms (PI3K-C2α, PI3K-C2β, and PI3K-C2γ) have distinct and non-overlapping cellular roles.

Inhalation of the prodrug PI3K inhibitor CL27c improves lung function in asthma and fibrosis.

PI3K activation plays a central role in the development of pulmonary inflammation and tissue remodeling. PI3K inhibitors may thus offer an improved therapeutic opportunity to treat non-resolving lung inflammation but their action is limited by unwanted on-target systemic toxicity. Here we present CL27c, a prodrug pan-PI3K inhibitor designed for local therapy, and investigate whether inhaled CL27c is effective in asthma and pulmonary fibrosis.

Structural determinants of Rab11 activation by the guanine nucleotide exchange factor SH3BP5.

The GTPase Rab11 plays key roles in receptor recycling, oogenesis, autophagosome formation, and ciliogenesis. However, investigating Rab11 regulation has been hindered by limited molecular detail describing activation by cognate guanine nucleotide exchange factors (GEFs). Here, we present the structure of Rab11 bound to the GEF SH3BP5, along with detailed characterization of Rab-GEF specificity.

Rab11 activity and PtdIns(3)P turnover removes recycling cargo from endosomes.

Directional transport of recycling cargo from early endosomes (EE) to the endocytic recycling compartment (ERC) relies on phosphatidylinositol 3-phosphate (PtdIns(3)P) hydrolysis and activation of the small GTPase Rab11. However, how these events are coordinated is yet unclear. By using a novel genetically-encoded FRET biosensor for Rab11, we report that generation of endosomal PtdIns(3)P by the clathrin-binding phosphoinositide 3-kinase class 2 alpha (PI3K-C2α) controls the activation of Rab11.

Phosphoinositide 3-Kinase Gamma Inhibition Protects From Anthracycline Cardiotoxicity and Reduces Tumor Growth.

Background: Anthracyclines, such as doxorubicin (DOX), are potent anticancer agents for the treatment of solid tumors and hematologic malignancies. However, their clinical use is hampered by cardiotoxicity. This study sought to investigate the role of phosphoinositide 3-kinase γ (PI3Kγ) in DOX-induced cardiotoxicity and the potential cardioprotective and anticancer effects of PI3Kγ inhibition.

Mitotic Spindle Assembly and Genomic Stability in Breast Cancer Require PI3K-C2α Scaffolding Function.

Proper organization of the mitotic spindle is key to genetic stability, but molecular components of inter-microtubule bridges that crosslink kinetochore fibers (K-fibers) are still largely unknown. Here we identify a kinase-independent function of class II phosphoinositide 3-OH kinase α (PI3K-C2α) acting as limiting scaffold protein organizing clathrin and TACC3 complex crosslinking K-fibers. Downregulation of PI3K-C2α causes spindle alterations, delayed anaphase onset, and aneuploidy, indicating that PI3K-C2α expression is required for genomic stability.

Identification of a Potent Phosphoinositide 3-Kinase Pan Inhibitor Displaying a Strategic Carboxylic Acid Group and Development of Its Prodrugs.

Activation of the phosphoinositide 3-kinase (PI3K) pathway is a key signaling event in cancer, inflammation, and other proliferative diseases. PI3K inhibitors are already approved for some specific clinical indications, but their systemic on-target toxicity limits their larger use. In particular, whereas toxicity is tolerable in acute treatment of life-threatening diseases, this is less acceptable in chronic conditions.

Therapeutic Targeting of PDEs and PI3K in Heart Failure with Preserved Ejection Fraction (HFpEF).

Purpose Of Review: Heart Failure with preserved Ejection Fraction (HFpEF) is a prevalent disease with considerable individual and societal burden. HFpEF patients often suffer from multiple pathological conditions thatcomplicate management and adversely affect outcome, including pulmonary hypertension and chronic obstructive pulmonary disease (COPD). To date, no treatment proved to be fully effective in reducing morbidity and mortality in HFpEF, possibly due to an incomplete understanding of the underlying molecular mechanisms.

The Guareschi Pyridine Scaffold as a Valuable Platform for the Identification of Selective PI3K Inhibitors.

A novel series of 4-aryl-3-cyano-2-(3-hydroxyphenyl)-6-morpholino-pyridines have been designed as potential phosphatidylinositol-3-kinase (PI3K) inhibitors. The compounds have been synthesized using the Guareschi reaction to prepare the key 4-aryl-3-cyano-2,6-dihydroxypyridine intermediate. A different selectivity according to the nature of the aryl group has been observed.

Phosphoinositide 3-Kinase-C2α Regulates Polycystin-2 Ciliary Entry and Protects against Kidney Cyst Formation.

Signaling from the primary cilium regulates kidney tubule development and cyst formation. However, the mechanism controlling targeting of ciliary components necessary for cilium morphogenesis and signaling is largely unknown. Here, we studied the function of class II phosphoinositide 3-kinase-C2α (PI3K-C2α) in renal tubule-derived inner medullary collecting duct 3 cells and show that PI3K-C2α resides at the recycling endosome compartment in proximity to the primary cilium base.

PI3K class II α controls spatially restricted endosomal PtdIns3P and Rab11 activation to promote primary cilium function.

Multiple phosphatidylinositol (PtdIns) 3-kinases (PI3Ks) can produce PtdIns3P to control endocytic trafficking, but whether enzyme specialization occurs in defined subcellular locations is unclear. Here, we report that PI3K-C2α is enriched in the pericentriolar recycling endocytic compartment (PRE) at the base of the primary cilium, where it regulates production of a specific pool of PtdIns3P. Loss of PI3K-C2α-derived PtdIns3P leads to mislocalization of PRE markers such as TfR and Rab11, reduces Rab11 activation, and blocks accumulation of Rab8 at the primary cilium.