scholarly journals Modulation of Rab5 and Rab7 Recruitment to Phagosomes by Phosphatidylinositol 3-Kinase

2003 ◽  
Vol 23 (7) ◽  
pp. 2501-2514 ◽  
Author(s):  
Otilia V. Vieira ◽  
Cecilia Bucci ◽  
Rene E. Harrison ◽  
William S. Trimble ◽  
Letizia Lanzetti ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Rab Gtpases ◽  
Phagosome Maturation ◽  
Phosphatidylinositol 3 Kinase ◽  
Pi3k Inhibitors ◽  
Late Endosomes ◽  
Site Of Action ◽  
Photobleaching Recovery ◽  
Lysosomal Protein ◽  
Phosphatidylinositol 3

ABSTRACT Phagosomal biogenesis is central for microbial killing and antigen presentation by leukocytes. However, the molecular mechanisms governing phagosome maturation are poorly understood. We analyzed the role and site of action of phosphatidylinositol 3-kinases (PI3K) and of Rab GTPases in maturation using both professional and engineered phagocytes. Rab5, which is recruited rapidly and transiently to the phagosome, was found to be essential for the recruitment of Rab7 and for progression to phagolysosomes. Similarly, functional PI3K is required for successful maturation. Remarkably, inhibition of PI3K did not preclude Rab5 recruitment to phagosomes but instead enhanced and prolonged it. Moreover, in the presence of PI3K inhibitors Rab5 was found to be active, as deduced from measurements of early endosome antigen 1 binding and by photobleaching recovery determinations. Though their ability to fuse with late endosomes and lysosomes was virtually eliminated by wortmannin, phagosomes nevertheless recruited a sizable amount of Rab7. Moreover, Rab7 recruited to phagosomes in the presence of PI3K antagonists retained the ability to bind its effector, Rab7-interacting lysosomal protein, suggesting that it is functionally active. These findings imply that (i) dissociation of Rab5 from phagosomes requires products of PI3K, (ii) PI3K-dependent effectors of Rab5 are not essential for the recruitment of Rab7 by phagosomes, and (iii) recruitment and activation of Rab7 are insufficient to induce fusion of phagosomes with late endosomes and lysosomes. Accordingly, transfection of constitutively active Rab7 did not bypass the block of phagolysosome formation exerted by wortmannin. We propose that Rab5 activates both PI3K-dependent and PI3K-independent effectors that act in parallel to promote phagosome maturation.

scholarly journals Phosphatidylinositol 3-kinase regulatory subunit 1 and phosphatase and tensin homolog as therapeutic targets in breast cancer

Tumor Biology ◽  
2017 ◽  
Vol 39 (3) ◽  
pp. 101042831769552 ◽  
Author(s):  
Ebubekir Dirican ◽  
Mustafa Akkiprik
Keyword(s):  
Breast Cancer ◽  
Cancer Progression ◽  
Molecular Mechanisms ◽  
Breast Cancer Progression ◽  
Regulatory Subunit ◽  
Phosphatidylinositol 3 Kinase ◽  
Phosphatase And Tensin Homolog ◽  
Tensin Homolog ◽  
Kinase Pathway ◽  
Phosphatidylinositol 3

Breast cancer is the most commonly diagnosed cancer among women in Turkey and worldwide. It is considered a heterogeneous disease and has different subtypes. Moreover, breast cancer has different molecular characteristics, behaviors, and responses to treatment. Advances in the understanding of the molecular mechanisms implicated in breast cancer progression have led to the identification of many potential therapeutic gene targets, such as Breast Cancer 1/2, phosphatidylinositol 3-kinase catalytic subunit alpha, and tumor protein 53. The aim of this review is to summarize the roles of phosphatidylinositol 3-kinase regulatory subunit 1 (alpha) (alias p85α) and phosphatase and tensin homolog in breast cancer progression and the molecular mechanisms involved. Phosphatase and tensin homolog is a tumor suppressor gene and protein. Phosphatase and tensin homolog antagonizes the phosphatidylinositol 3-kinase/AKT signaling pathway that plays a key role in cell growth, differentiation, and survival. Loss of phosphatase and tensin homolog expression, detected in about 20%–30% of cases, is known to be one of the most common tumor changes leading to phosphatidylinositol 3-kinase pathway activation in breast cancer. Instead, the regulatory subunit p85α is a significant component of the phosphatidylinositol 3-kinase pathway, and it has been proposed that a reduction in p85α protein would lead to decreased negative regulation of phosphatidylinositol 3-kinase and hyperactivation of the phosphatidylinositol 3-kinase pathway. Phosphatidylinositol 3-kinase regulatory subunit 1 protein has also been reported to be a positive regulator of phosphatase and tensin homolog via the stabilization of this protein. A functional genetic alteration of phosphatidylinositol 3-kinase regulatory subunit 1 that results in reduced p85α protein expression and increased insulin receptor substrate 1 binding would lead to enhanced phosphatidylinositol 3-kinase signaling and hence cancer development. Phosphatidylinositol 3-kinase regulatory subunit 1 underexpression was observed in 61.8% of breast cancer samples. Therefore, expression/alternations of phosphatidylinositol 3-kinase regulatory subunit 1 and phosphatase and tensin homolog genes have crucial roles for breast cancer progression. This review will summarize the biological roles of phosphatidylinositol 3-kinase regulatory subunit 1 and phosphatase and tensin homolog in breast cancer, with an emphasis on recent findings and the potential of phosphatidylinositol 3-kinase regulatory subunit 1 and phosphatase and tensin homolog as a therapeutic target for breast cancer therapy.

Hepatic glutamine transporter activation in burn injury: role of amino acids and phosphatidylinositol-3-kinase

2000 ◽  
Vol 278 (4) ◽  
pp. G532-G541 ◽  
Author(s):  
Timothy M. Pawlik ◽  
Rüdiger Lohmann ◽  
Wiley W. Souba ◽  
Barrie P. Bode
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Burn Injury ◽  
Cell Swelling ◽  
Phosphatidylinositol 3 Kinase ◽  
Pi3k Inhibitors ◽  
Glutamine Transporter ◽  
Hypermetabolic State ◽  
Phosphatidylinositol 3

Burn injury elicits a marked, sustained hypermetabolic state in patients characterized by accelerated hepatic amino acid metabolism and negative nitrogen balance. The transport of glutamine, a key substrate in gluconeogenesis and ureagenesis, was examined in hepatocytes isolated from the livers of rats after a 20% total burn surface area full-thickness scald injury. A latent and profound two- to threefold increase in glutamine transporter system N activity was first observed after 48 h in hepatocytes from injured rats compared with controls, persisted for 9 days, and waned toward control values after 18 days, corresponding with convalescence. Further studies showed that the profound increase was fully attributable to rapid posttranslational transporter activation by amino acid-induced cell swelling and that this form of regulation may be elicited in part by glucagon. The phosphatidylinositol-3-kinase (PI3K) inhibitors wortmannin and LY-294002 each significantly attenuated transporter stimulation by amino acids. The data suggest that PI3K-dependent system N activation by amino acids may play an important role in fueling accelerated hepatic nitrogen metabolism after burn injury.

scholarly journals Transcriptional regulation of human mucin MUC4 by bile acids in oesophageal cancer cells is promoter-dependent and involves activation of the phosphatidylinositol 3-kinase signalling pathway

2004 ◽  
Vol 377 (3) ◽  
pp. 701-708 ◽  
Author(s):  
Christophe MARIETTE ◽  
Michaël PERRAIS ◽  
Emmanuelle LETEURTRE ◽  
Nicolas JONCKHEERE ◽  
Brigitte HÉMON ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Bile Acids ◽  
Oesophageal Cancer ◽  
Molecular Mechanisms ◽  
Complex Mixture ◽  
Transcriptional Level ◽  
Mrna Levels ◽  
Phosphatidylinositol 3 Kinase ◽  
Mucin Gene ◽  
Phosphatidylinositol 3

Abnormal gastro-oesophageal reflux and bile acids have been linked to the presence of Barrett's oesophageal premalignant lesion associated with an increase in mucin-producing goblet cells and MUC4 mucin gene overexpression. However, the molecular mechanisms underlying the regulation of MUC4 by bile acids are unknown. Since total bile is a complex mixture, we undertook to identify which bile acids are responsible for MUC4 up-regulation by using a wide panel of bile acids and their conjugates. MUC4 apomucin expression was studied by immunohistochemistry both in patient biopsies and OE33 oesophageal cancer cell line. MUC4 mRNA levels and promoter regulation were studied by reverse transcriptase–PCR and transient transfection assays respectively. We show that among the bile acids tested, taurocholic, taurodeoxycholic, taurochenodeoxycholic and glycocholic acids and sodium glycocholate are strong activators of MUC4 expression and that this regulation occurs at the transcriptional level. By using specific pharmacological inhibitors of mitogen-activated protein kinase, phosphatidylinositol 3-kinase, protein kinase A and protein kinase C, we demonstrate that bile acid-mediated up-regulation of MUC4 is promoter-specific and mainly involves activation of phosphatidylinositol 3-kinase. This new mechanism of regulation of MUC4 mucin gene points out an important role for bile acids as key molecules in targeting MUC4 overexpression in early stages of oesophageal carcinogenesis.

scholarly journals Rabenosyn-5, a Novel Rab5 Effector, Is Complexed with Hvps45 and Recruited to Endosomes through a Fyve Finger Domain

2000 ◽  
Vol 151 (3) ◽  
pp. 601-612 ◽  
Author(s):  
Erik Nielsen ◽  
Savvas Christoforidis ◽  
Sandrine Uttenweiler-Joseph ◽  
Marta Miaczynska ◽  
Frederique Dewitte ◽  
...  
Keyword(s):  
Early Endosome ◽  
Effector Proteins ◽  
Endosomal Trafficking ◽  
Membrane Domains ◽  
Phosphatidylinositol 3 Kinase ◽  
Early Endosomes ◽  
Site Of Action ◽  
Endosomal Membranes ◽  
Novel Protein ◽  
Phosphatidylinositol 3

Rab5 regulates endocytic membrane traffic by specifically recruiting cytosolic effector proteins to their site of action on early endosomal membranes. We have characterized a new Rab5 effector complex involved in endosomal fusion events. This complex includes a novel protein, Rabenosyn-5, which, like the previously characterized Rab5 effector early endosome antigen 1 (EEA1), contains an FYVE finger domain and is recruited in a phosphatidylinositol-3-kinase–dependent fashion to early endosomes. Rabenosyn-5 is complexed to the Sec1-like protein hVPS45. hVPS45 does not interact directly with Rab5, therefore Rabenosyn-5 serves as a molecular link between hVPS45 and the Rab5 GTPase. This property suggests that Rabenosyn-5 is a closer mammalian functional homologue of yeast Vac1p than EEA1. Furthermore, although both EEA1 and Rabenosyn-5 are required for early endosomal fusion, only overexpression of Rabenosyn-5 inhibits cathepsin D processing, suggesting that the two proteins play distinct roles in endosomal trafficking. We propose that Rab5-dependent formation of membrane domains enriched in phosphatidylinositol-3-phosphate has evolved as a mechanism for the recruitment of multiple effector proteins to mammalian early endosomes, and that these domains are multifunctional, depending on the differing activities of the effector proteins recruited.

scholarly journals A vesicle surface tyrosine kinase regulates phagosome maturation

2007 ◽  
Vol 178 (3) ◽  
pp. 411-423 ◽  
Author(s):  
Jun Fang ◽  
Joseph A. Brzostowski ◽  
Stephen Ou ◽  
Nilgun Isik ◽  
Vinod Nair ◽  
...  
Keyword(s):  
Tyrosine Kinase ◽  
Receptor Tyrosine Kinase ◽  
Molecular Mechanisms ◽  
Control Mechanism ◽  
Kinase Domain ◽  
Microbial Pathogens ◽  
Phagosome Maturation ◽  
Tyrosine Kinase Signaling ◽  
Late Endosomes

Phagocytosis is crucial for host defense against microbial pathogens and for obtaining nutrients in Dictyostelium discoideum. Phagocytosed particles are delivered via a complex route from phagosomes to lysosomes for degradation, but the molecular mechanisms involved in the phagosome maturation process are not well understood. Here, we identify a novel vesicle-associated receptor tyrosine kinase-like protein, VSK3, in D. discoideum. We demonstrate how VSK3 is involved in phagosome maturation. VSK3 resides on the membrane of late endosomes/lysosomes with its C-terminal kinase domain facing the cytoplasm. Inactivation of VSK3 by gene disruption reduces the rate of phagocytosis in cells, which is rescued by re-expression of VSK3. We found that the in vivo function of VSK3 depends on the presence of the kinase domain and vesicle localization. Furthermore, VSK3 is not essential for engulfment, but instead, is required for the fusion of phagosomes with late endosomes/lysosomes. Our findings suggest that localized tyrosine kinase signaling on the surface of endosome/lysosomes represents a control mechanism for phagosome maturation.

scholarly journals Managing toxicities of phosphatidylinositol-3-kinase (PI3K) inhibitors

Hematology ◽  
2020 ◽  
Vol 2020 (1) ◽  
pp. 346-356
Author(s):  
Ashley Hanlon ◽  
Danielle M. Brander
Keyword(s):  
Late Onset ◽  
Pi3k Pathway ◽  
Lymphocytic Leukemia ◽  
Phosphatidylinositol 3 Kinase ◽  
Small Lymphocytic Lymphoma ◽  
Pi3k Inhibitors ◽  
Novel Treatment ◽  
Immune Mediated ◽  
The Common ◽  
Phosphatidylinositol 3

Abstract Despite the proven effective approach to targeting the phosphatidylinositol-3-kinase (PI3K) pathway in B-cell malignancies, the approved PI3K inhibitors idelalisib and duvelisib have been less commonly selected for patients with chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL), given the availability of other more tolerable agents. However, patients with CLL/SLL can experience a disease course that is multiply relapsed, refractory, or intolerant to treatment, and PI3K inhibitors can achieve meaningful responses. This article reviews the common early- and late-onset (considered immune-mediated) toxicities with PI3K inhibitors, including infections, hepatotoxicity, diarrhea and/or colitis, and pneumonitis. Data on pretreatment considerations, toxicity management, and drug rechallenge are presented. In addition, next-generation PI3K inhibitors and novel treatment approaches with PI3K inhibitors, including combinations, time-limited treatments, and intermittent dosing, are highlighted.

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