ESCRT Machinery Potentiates HIV-1 Utilization of the PI(4,5)P2-PLC-IP3R-Ca2+ Signaling Cascade

Ehrlich, Lorna S.; Medina, Gisselle N.; Carter, Carol A.

doi:10.1016/j.jmb.2011.08.038

Cited by 19 publications

(38 citation statements)

References 63 publications

(94 reference statements)

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“…Several previous studies indicated that intracellular Ca 2ϩ levels modulate HIV-1 Gag trafficking and assembly, presumably by regulating exocytic events (23,24,33,54). It is possible that AP-3 mediates HIV-1 Gag trafficking to the PM along the secretory pathway, which is regulated by intracellular Ca 2ϩ signaling.…”

Section: Discussionmentioning

confidence: 99%

Defective HIV-1 Particle Assembly in AP-3-Deficient Cells Derived from Patients with Hermansky-Pudlak Syndrome Type 2

Liu

Sutton

Woodruff

et al. 2012

J Virol

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bAdaptor protein complex 3 (AP-3) is a heterotetramer that is involved in signal-mediated protein sorting to endosomal-lysosomal organelles. AP-3 deficiency in humans, induced by mutations in the AP3B1 gene, which encodes the ␤3A subunit of the AP-3 complex, results in Hermansky-Pudlak syndrome 2 (HPS2), which is a rare genetic disorder with defective lysosome-related organelles. In a previous study, we identified the AP-3 complex as an important contributor to HIV-1 assembly and release. We hypothesized that cells from patients affected by HPS2 should demonstrate abnormalities of HIV-1 assembly. Here we report that HIV-1 particle assembly and release are indeed diminished in HPS2 fibroblast cultures. Transient or stable expression of the full-length wild-type ␤3A subunit in HPS2 fibroblasts restored the impaired virus assembly and release. In contrast, virus-like particle release mediated by MA-deficient Gag mutants lacking the AP-3 binding site was not altered in HPS2 cells, indicating that the MA domain serves as the major viral determinant required for the recruitment of the AP-3 complex. AP-3 deficiency decreased HIV-1 Gag localization at the plasma membrane and late endosomes and increased the accumulation of HIV-1 Gag at an intermediate step between early and late endosomes. Blockage of the clathrin-mediated endocytic pathway in HPS2 cells did not reverse the inhibited virus assembly and release imposed by the AP-3 deficiency. These results demonstrate that the intact and stable AP-3 complex is required for HIV-1 assembly and release, and the involvement of the AP-3 complex in late stages of the HIV-1 replication cycle is independent of clathrin-mediated endocytosis.

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Section: Discussionmentioning

confidence: 99%

Defective HIV-1 Particle Assembly in AP-3-Deficient Cells Derived from Patients with Hermansky-Pudlak Syndrome Type 2

Liu

Sutton

Woodruff

et al. 2012

J Virol

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“…We (Ehrlich et al, 2011) previously provided evidence that [Ca 2+ ] i in cells expressing WT Gag was higher than in mock-treated cells or in cells expressing a budding-defective Gag mutant. The mutant, P7L-Gag, possesses a single residue change in the primary L domain (P 7 TAP to L 7 TAP) that impairs Tsg101 binding to the site (Demirov et al, 2002).…”

Section: Resultsmentioning

confidence: 96%

Tsg101 regulates PI(4,5)P2/Ca2+ signaling for HIV-1 Gag assembly

et al. 2014

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Our previous studies identified the 1,4,5-inositol trisphosphate receptor (IP3R), a channel mediating release of Ca2+ from ER stores, as a cellular factor differentially associated with HIV-1 Gag that might facilitate ESCRT function in virus budding. Channel opening requires activation that is initiated by binding of 1,4,5-triphosphate (IP3), a product of phospholipase C (PLC)-mediated PI(4,5)P2 hydrolysis. The store emptying that follows stimulates store refilling which requires intact PI(4,5)P2. Raising cytosolic Ca2+ promotes viral particle production and our studies indicate that IP3R and the ER Ca2+ store are the physiological providers of Ca2+ for Gag assembly and release. Here, we show that Gag modulates ER store gating and refilling. Cells expressing Gag exhibited a higher cytosolic Ca2+ level originating from the ER store than control cells, suggesting that Gag induced release of store Ca2+. This property required the PTAP motif in Gag that recruits Tsg101, an ESCRT-1 component. Consistent with cytosolic Ca2+ elevation, Gag accumulation at the plasma membrane was found to require continuous IP3R activation. Like other IP3R channel modulators, Gag was detected in physical proximity to the ER and to endogenous IP3R, as indicated respectively by total internal reflection fluorescence (TIRF) and immunoelectron microscopy (IEM) or indirect immunofluorescence. Reciprocal co-immunoprecipitation suggested that Gag and IP3R proximity is favored when the PTAP motif in Gag is intact. Gag expression was also accompanied by increased PI(4,5)P2 accumulation at the plasma membrane, a condition favoring store refilling capacity. Supporting this notion, Gag particle production was impervious to treatment with 2-aminoethoxydiphenyl borate, an inhibitor of a refilling coupling interaction. In contrast, particle production by a Gag mutant lacking the PTAP motif was reduced. We conclude that a functional PTAP L domain, and by inference Tsg101 binding, confers Gag with an ability to modulate both ER store Ca2+ release and ER store refilling.

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“…The observation that this compound exerts a strong inhibitory effect in a reporter-gene virus-infectivity assay suggests that PI-PLC may also have a role in postfusion events. Ehrlich et al [150] investigated the role of PI-PLC signaling in HIV-1 release, demonstrating that U-73122 inhibits Gag trafficking and viral-particle release by blocking the PI-PLC-catalyzed hydrolysis of PIP 2 to generate IP 3 , thus inhibiting IP3R activation [151]. They also showed that m-3M3-FBS [2,4,6-trimethyl-N-(meta-3-trifluoromethyl-pheny)benzenesulfonamide], a stimulator of PI-PLC activity that increases cellular IP 3 and cytosolic Ca 2 , enhances viral-particle release [151].…”

Section: Plcs In Hiv-1 Infectionmentioning

confidence: 99%

Phospholipases: at the crossroads of the immune system and the pathogenesis of HIV-1 infection

Cecchetti

Spadaro

Gessani

et al. 2016

Journal of Leukocyte Biology

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Multiple host factors and their interactions with viral proteins contribute to the complexity of HIV-1 pathogenesis and disease progression. The virus exploits the cell-signaling networks to prepare the ground for viral replication, to affect functions of either infected or uninfected bystander cells, and to evade the immune response. These events are hallmarks of HIV-1 pathogenesis that lead toward AIDS. Phospholipases are essential mediators of intracellular and intercellular signaling. They function as phospholipid-hydrolyzing enzymes, generating many bioactive lipid mediators or second messengers, which control multiple cellular functions, thus regulating a variety of physiologic and pathophysiologic processes. These enzymes also represent important components of the cell-signaling networks exploited by HIV-1 and its proteins to favor viral replication and persistence, as well as immune response dysfunction. Although some individual phospholipases were studied in the context of HIV-1 infection, the mechanisms whereby they regulate diverse infection-associated processes, as well as the interaction among different phospholipases have yet to be fully elucidated. In this review, we discuss the principal aspects of the complex interaction between phospholipases, HIV-1, and the immune system. A thorough understanding of the signaling networks that involve phospholipases in both HIV-1-infected cells and individuals is essential to determine whether therapeutic targeting of these enzymes may represent a novel approach to control viral replication, as well as the associated inflammation and comorbidities.

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ESCRT Machinery Potentiates HIV-1 Utilization of the PI(4,5)P2-PLC-IP3R-Ca2+ Signaling Cascade

Cited by 19 publications

References 63 publications

Defective HIV-1 Particle Assembly in AP-3-Deficient Cells Derived from Patients with Hermansky-Pudlak Syndrome Type 2

Defective HIV-1 Particle Assembly in AP-3-Deficient Cells Derived from Patients with Hermansky-Pudlak Syndrome Type 2

Tsg101 regulates PI(4,5)P2/Ca2+ signaling for HIV-1 Gag assembly

Phospholipases: at the crossroads of the immune system and the pathogenesis of HIV-1 infection

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