TRPP2 dysfunction decreases ATP-evoked calcium, induces cell aggregation and stimulates proliferation in T lymphocytes

Abstract

Background Autosomal dominant polycystic kidney disease (ADPKD) is mainly characterised by the development and enlargement of renal cysts that lead to end-stage renal disease (ESRD) in adult patients. Other clinical manifestations of this pathology include hypertension, haematuria, abdominal pain, cardiovascular system alterations and intracranial aneurysms. ADPKD is linked to mutations in either PKD1 or PKD2 that codifies polycystin-1 (PC1) and polycystin-2 (PC2 or TRPP2), respectively. PC1 and TRPP2 are membrane proteins that function as receptor-channel elements able to regulate calcium homeostasis. The function of polycystins has been mainly studied in kidney cells; but the role of these proteins in T lymphocytes is not well defined. Methods T lymphocytes were produced from ADPKD1 and ADPKD2 patients as well as from non-ADPKD subjects undergoing renal replacement therapy (RRT) and healthy controls. Protein expression and phosphorylation levels were analysed by western blotting, cell proliferation was calculated by direct counting using trypan blue assay and intracellular calcium concentration was measured by Fura-2 method. Results PKD2 mutations lead to the significant reduction of TRPP2 expression in T lymphocytes derived from ADPKD patients. Furthermore, a smaller TRPP2 truncated protein in T lymphocytes of patients carrying the mutation R872X in PKD2 was also observed, suggesting that TRPP2 mutated proteins may be stably expressed. The silencing or mutation of PKD2 causes a strong reduction of ATP-evoked calcium in Jurkat cells and ADPKD2 T lymphocytes, respectively. Moreover, T lymphocytes derived from both ADPKD1 and ADPKD2 patients show increased cell proliferation, basal chemotaxis and cell aggregation compared with T lymphocytes from non-ADPKD subjects. Similarly to observations made in kidney cells, mutations in PKD1 and PKD2 dysregulate ERK, mTOR, NFkB and MIF pathways in T lymphocytes. Conclusions Because the alteration of ERK, mTOR, NFkB and MIF signalling found in T lymphocytes of ADPKD patients may contribute to the development of interstitial inflammation promoting cyst growth and kidney failure (ESRD), the targeting of inflammasome proteins could be an intriguing option to delay the progression of ADPKD.

Serum Copeptin, NLPR3, and suPAR Levels among Patients with Autosomal-Dominant Polycystic Kidney Disease with and without Impaired Renal Function

“…No other study has evaluated the levels of NLRP3 in patients with ADPKD in vivo. The only relevant evidence derives from a study in which the expression and phosphorylation levels of several proteins, but not NLRP3, participating in the inflammasome were evaluated on T lymphocytes produced in ADPKD patients with PKD1 or PKD2 gene mutations and non-ADPKD subjects [24]. The study showed that ADPKD-derived cells presented increased cell proliferation, basal chemotaxis, and cell aggregation.…”

Insights Into the Molecular Mechanisms of Polycystic Kidney Diseases

“…Specifically, it has been proposed that activation of adaptive immunity can be used as a biomarker for ADPKD: increased levels of interleukins (IL-23, IL-6, and, in particular, IL-17) in serum and urine in ADPKD patients and enhanced expression of SEMA7A (Semaphorin 7A) protein on immune cells ( Soleimani et al, 2015 ; Lee et al, 2018 ). Interestingly, B-lymphoblastoid cells (LCL) obtained from ADPKD patients express genes encoding PC1 and PC2, and their T-cells also express PC1 and PC2, although at a lower level compared with LCL ( Aguiari et al, 2004 ; Magistroni et al, 2019 ). Furthermore, in patients carrying the PKD2 mutation, Ca 2+ signaling was found to be impaired in circulating T-cells; T-cells derived from both patients with PKD1 and PKD2 mutations demonstrated increased proliferation and increased homotypic T-cell aggregation ( Magistroni et al, 2019 ).…”

“…Interestingly, B-lymphoblastoid cells (LCL) obtained from ADPKD patients express genes encoding PC1 and PC2, and their T-cells also express PC1 and PC2, although at a lower level compared with LCL ( Aguiari et al, 2004 ; Magistroni et al, 2019 ). Furthermore, in patients carrying the PKD2 mutation, Ca 2+ signaling was found to be impaired in circulating T-cells; T-cells derived from both patients with PKD1 and PKD2 mutations demonstrated increased proliferation and increased homotypic T-cell aggregation ( Magistroni et al, 2019 ). To date, there are still many uncertainties about the participation of cells of adaptive and innate immunity in PKD.…”

Purinergic and Adenosinergic Signaling in Pancreatobiliary Diseases

“…P2XR affinity is generally in the low micromolar range and highly sensitive to sudden changes in local ATP concentrations. P2X7R is the exception and has a remarkably high tetrabasic ATP activation threshold in the millimolar range ( North and Surprenant, 2000 ; Magistroni et al, 2019 ). Active release of ATP to the extracellular compartment is tightly mediated by connexins, pannexins, and exocytosis, which are predominantly regulated by P2XR-dependent feedback loops ( Di Virgilio et al, 2020 ; Li et al, 2020 ).…”