Dataset Information

The tuberous sclerosis proteins regulate formation of the primary cilium via a rapamycin-insensitive and polycystin 1-independent pathway.

ABSTRACT: Tuberous sclerosis complex (TSC) is a tumor suppressor gene syndrome in which severe renal cystic disease can occur. Many renal cystic diseases, including autosomal dominant polycystic kidney disease (ADPKD), are associated with absence or dysfunction of the primary cilium. We report here that hamartin (TSC1) localizes to the basal body of the primary cilium, and that Tsc1(-/-) and Tsc2(-/-) mouse embryonic fibroblasts (MEFs) are significantly more likely to contain a primary cilium than wild-type controls. In addition, the cilia of Tsc1(-/-) and Tsc2(-/-) MEFs are 17-27% longer than cilia from wild-type MEFs. These data suggest a novel type of ciliary disruption in TSC, associated with enhanced cilia development. The TSC1 and TSC2 proteins function as a heterodimer to inhibit the activity of the mammalian target of rapamycin complex 1 (TORC1). The enhanced ciliary formation in the Tsc1(-/-) and Tsc2(-/-) MEFs was not abrogated by rapamycin, which indicates a TORC1-independent mechanism. Polycystin 1 (PC1), the product of the PKD1 gene, has been found to interact with TSC2, but Pkd1(-/-) MEFs did not have enhanced ciliary formation. Furthermore, while activation of mTOR has been observed in renal cysts from ADPKD patients, Pkd1(-/-) MEFs did not have evidence of constitutive mTOR activation, thereby underscoring the independent functions of the TSC proteins and PC1 in regulation of primary cilia and mTOR. Our data link the TSC proteins with the primary cilium and reveal a novel phenotype of enhanced ciliary formation in a cyst-associated disease.

SUBMITTER: Hartman TR

PROVIDER: S-EPMC2644647 | biostudies-literature | 2009 Jan

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

The tuberous sclerosis proteins regulate formation of the primary cilium via a rapamycin-insensitive and polycystin 1-independent pathway.

Hartman Tiffiney R TR Liu Dongyan D Zilfou Jack T JT Robb Victoria V Morrison Tasha T Watnick Terry T Henske Elizabeth P EP

Human molecular genetics 20081009 1

Tuberous sclerosis complex (TSC) is a tumor suppressor gene syndrome in which severe renal cystic disease can occur. Many renal cystic diseases, including autosomal dominant polycystic kidney disease (ADPKD), are associated with absence or dysfunction of the primary cilium. We report here that hamartin (TSC1) localizes to the basal body of the primary cilium, and that Tsc1(-/-) and Tsc2(-/-) mouse embryonic fibroblasts (MEFs) are significantly more likely to contain a primary cilium than wild-ty ...[more]

PMID: 18845692

Similar Datasets

Project description:Tuberous sclerosis syndrome (TSC) is an autosomal dominant tumor suppressor gene syndrome affecting multiple organs, including renal angiomyolipomas and pulmonary lymphangioleiomyomatosis (LAM). LAM is a female-predominant interstitial lung disease characterized by the progressive cyst formation and respiratory failure, which is also seen in sporadic patients without TSC. Mutations in TSC1 or TSC2 cause TSC, result in hyperactivation of mammalian target of rapamycin (mTOR), and are also seen in LAM cells in sporadic LAM. We recently reported that prostaglandin biosynthesis and cyclooxygenase-2 were deregulated in TSC and LAM. Phospholipase A2 (PLA2) is the rate-limiting enzyme that catalyzes the conversion of plasma membrane phospholipids into prostaglandins. In this study, we identified upregulation of adipocyte AdPLA2 (PLA2G16) in LAM nodule cells using publicly available expression data. We showed that the levels of AdPLA2 transcript and protein were higher in LAM lungs compared with control lungs. We then showed that TSC2 negatively regulates the expression of AdPLA2, and loss of TSC2 is associated with elevated production of prostaglandin E2 (PGE2) and prostacyclin (PGI2) in cell culture models. Mouse model studies also showed increased expression of AdPLA2 in xenograft tumors, estrogen-induced lung metastatic lesions of Tsc2 null leiomyoma-derived cells, and spontaneous renal cystadenomas from Tsc2+/- mice. Importantly, rapamycin treatment did not affect the expression of AdPLA2 and the production of PGE2 by TSC2-deficient mouse embryonic fibroblast (Tsc2-/-MEFs), rat uterine leiomyoma-derived ELT3 cells, and LAM patient-associated renal angiomyolipoma-derived "mesenchymal" cells. Furthermore, methyl arachidonyl fluorophosphate (MAFP), a potent irreversible PLA2 inhibitor, selectively suppressed the growth and induced apoptosis of TSC2-deficient LAM patient-derived cells relative to TSC2-addback cells. Our findings suggest that AdPLA2 plays an important role in promoting tumorigenesis and disease progression by modulating the production of prostaglandins and may serve as a potential therapeutic target in TSC and LAM.

Project description:Tuberous sclerosis complex (TSC) is an inherited multi-system disorder caused by mutations in the TSC1 or TSC2 gene. TSC patients are often diagnosed with a range of neurodevelopmental (ND) manifestations termed TSC-associated neuropsychiatric disorders (TAND) including autism spectrum disorder (ASD), intellectual disability (ID), anxiety and mood disorders. Hamartin (TSC1) and tuberin (TSC2) proteins form a complex inhibiting mechanistic target of rapamycin complex 1 (mTORC1) kinase signaling. Loss of TSC1 or TSC2 activates mTORC1 that, among several targets, controls protein synthesis by inhibiting translational repressor eIF4E-binding proteins. Using neural progenitor cells (NPCs) from patient-derived induced pluripotent stem cells (iPSCs), we recently reported early ND phenotypic changes, including increased cell proliferation and altered neurite outgrowth in CRISPR-modified TSC1-null NPCs, which were unaffected by mTORC1 inhibition by rapamycin,the only approved therapy for TSC1. Here, to assess TSC1-dependent gene expression programs in NPCs, we used polysome-profiling, which quantifies changes in mRNA abundance and translational efficiencies at a transcriptome-wide level. In addition to changes in mRNA abundance, this revealed numerous TSC1-dependent alterations in translational efficiencies. To assess the relevance of these gene expression alterations we performed polysome-profiling in post-mortem brains originating from ASD donors and matched controls. Strikingly, TSC1-dependent alterations in mRNA translation observed in NPCs were largely recapitulated in human brains. Furthermore, although polysome-profiling revealed a partial reversal of TSC1-associated gene expression alterations following rapamycin treatment, most genes related to neural activity/synaptic regulation or ASD that showed TSC1-dependent translation were rapamycin-insensitive. Therefore, we also examined whether early ND rapamycin-insensitive phenotypes in TSC1-null NPCs could be rescued by a third-generation bi-steric, mTORC1-selective inhibitor RMC-6272 (Revolution Medicines, Inc.). Unlike rapamycin, RMC-6272 strongly inhibited translation and reversed TSC1-associated proliferation and neurite outgrowth phenotypes. In summary, we reveal ample translational alterations in TSC1 patient-derived NPCs recapitulating human brain expression profiles and potential implications for treatment of TAND.

Project description:Tuberous sclerosis (TS) is a rare autosomal dominant systemic disease with an estimated prevalence of 1/6000. Renal angiomyolipoma (AML) is a benign tumour with high morbidity frequently present in TS. The aim of the study was to test the effect of rapamycin in reducing the volume of AML in TS.Twenty four-month prospective open-label, single arm, unicentre Phases II andIII study. The primary endpoint was to evaluate the effect of treatment on the reduction of at least 50% AML volume from baseline at 24 months. The secondary endpoints were: average tumour reduction, surgical complications, skin lesions and drug safety.The study population comprised 17 patients, aged >10 years who were diagnosed with TS and had ?1 renal AML >2 cm of diameter and had a serum creatinine < 2mg/dl and urine protein/creatinine ratio < 22.6 mg/mmol. The trial was conducted at Fundació Puigvert. Rapamycin was given to achieve stable plasma levels between 4 and 8 ng/ml. AML volume was estimated using orthogonal measurements by MRI at baseline, 6, 12 and 24 months.Ten out of 17 patients were success responders for the main outcome -58.8%, 95%CI: 32.9% to 81.6%-. After 6 months of therapy, the mean volume decrease was 55.18% (5.01 standard error (SE); p<0.001) and 66.38% (4.41 SE; p<0.001) at year 1. There was no significant decrease between year 1 and 2. According to RECIST criteria, all patients achieved a partial response at year 1 and all but two had already achieved this partial response after 6 months.The main analysis was performed according to the intention-to-treat principle analysis. Tumour volume was analyzed over time by means of mixed models for repeated measurement analysis. We used the baseline tumour volume as a covariate for the absolute change and percentage change from baseline data. The analysis was performed using SAS version 9.2 software, and the level of significance was established at 0.05 (two-sided).This study show that mTOR inhibitors are a relatively safe, efficacious and less aggressive alternative than currently available options in the management of AML in TS.EudraCT number: 2007-005978-30, ClinicalTrials.gov number: NCT0121712.

Dataset Information

The tuberous sclerosis proteins regulate formation of the primary cilium via a rapamycin-insensitive and polycystin 1-independent pathway.

Publications

The tuberous sclerosis proteins regulate formation of the primary cilium via a rapamycin-insensitive and polycystin 1-independent pathway.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets