ABSTRACT
The primary cilium, hereafter cilium, is an antenna-like organelle that modulates intracellular responses, including autophagy, a lysosomal degradation process essential for cell homeostasis. Dysfunction of the cilium is associated with impairment of autophagy and diseases known as "ciliopathies". The discovery of autophagy-related proteins at the base of the cilium suggests its potential role in coordinating autophagy initiation in response to physiopathological stimuli. One of these proteins, beclin-1 (BECN1), it which is necessary for autophagosome biogenesis. Additionally, polycystin-2 (PKD2), a calcium channel enriched at the cilium, is required and sufficient to induce autophagy in renal and cancer cells. We previously demonstrated that PKD2 and BECN1 form a protein complex at the endoplasmic reticulum in non-ciliated cells, where it initiates autophagy, but whether this protein complex is present at the cilium remains unknown. Anorexigenic pro-opiomelanocortin (POMC) neurons are ciliated cells that require autophagy to maintain intracellular homeostasis. POMC neurons are sensitive to metabolic changes, modulating signaling pathways crucial for controlling food intake. Exposure to the saturated fatty acid palmitic acid (PA) reduces ciliogenesis and inhibits autophagy in these cells. Here, we show that PKD2 and BECN1 form a protein complex in N43/5 cells, an in vitro model of POMC neurons, and that both PKD2 and BECN1 locate at the cilium. In addition, our data show that the cilium is required for PKD2-BECN1 protein complex formation and that PA disrupts the PKD2-BECN1 complex, suppressing autophagy. Our findings provide new insights into the mechanisms by which the cilium controls autophagy in hypothalamic neuronal cells.
Subject(s)
Autophagy , Beclin-1 , Cilia , Hypothalamus , Neurons , TRPP Cation Channels , Animals , Mice , Beclin-1/metabolism , Cilia/metabolism , Hypothalamus/metabolism , Hypothalamus/cytology , Neurons/metabolism , TRPP Cation Channels/metabolism , TRPP Cation Channels/geneticsABSTRACT
Human Cytomegalovirus (HCMV) is a frequent opportunistic pathogen in immunosuppressed patients, which can be involved in kidney allograft dysfunction and rejection. In order to study the pathophysiology of HCMV renal diseases, we concentrated on the impact of HCMV infection on human renal tubular epithelial HK-2 cells. Our aim was to develop a model of infection of HK-2 cells by using the viral strain TB40/E, that contains the extended cell tropism of clinical isolates and the efficient viral multiplication in cell culture of laboratory-adapted strains. We observed that HK-2 cells can be infected by HCMV and expressed viral antigens, but they do not produce extracellular viral particles. We then studied the interplay of HCMV with ciliogenesis and autophagy. Primary cilium (PC) is a stress sensor important to maintain renal tissue homeostasis that projects from the apical side into the lumen of tubule cells. PC formation and length were not modified by HCMV infection. Autophagy, another stress response process critically required for normal kidney functions, was inhibited by HCMV in HK-2 cells with a reduction in the autophagic flux. HCMV classically induces an enlargement of infected cells in vivo and in vitro, and we observed that HCMV infection led to an enlargement of the HK-2 cell volume. Our results constitute therefore an excellent starting point to further explore the role of these mechanisms in renal cells dysfunction.
Subject(s)
Cytomegalovirus Infections , Cytomegalovirus , Autophagy , Cells, Cultured , Epithelial Cells , HumansABSTRACT
The classical description of the neural elements that compose the lining of brain ventricles introduces us to the single layer of ependymal cells. However, new findings, especially in the lateral ventricle (LV)-the major niche for the generation of new neurons in the adult brain-have provided information about additional cell elements that influence the organization of this part of the ventricular system and produce important contributions to neurogenesis. To complement the cell neurochemistry findings, we present a three-dimensional in situ description that demonstrates the anatomical details of the different types of ciliated cells and the innervation of these elements. After processing adult rat brains for ultrastructural analysis by high-resolution scanning electron microscopy (HRSEM) and transmission electron microscopy, we observed a heterogeneous pattern of cilia distribution at the different poles of the LV surface. Furthermore, we describe the particular three-dimensional aspects of the ciliated cells of the LV, in addition the fiber bundles and varicose axons surrounding these cells. Therefore, we provide a unique ultrastructural description of the three-dimensional in situ organization of the LV surface, highlighting its innervation, to corroborate the available neurochemical and functional findings regarding the factors that regulate this neurogenic niche.
ABSTRACT
Autosomal dominant polycystic kidney disease (ADPKD), a most common genetic cause of chronic renal failure, is characterized by the progressive development and enlargement of cysts in kidneys and other organs. The cystogenic process is highly complex and involves a high proliferative rate, increased apoptosis, altered protein sorting, changed secretory characteristics, and disorganization of the extracellular matrix. ADPKD is caused by mutations in the genes encoding polycystin-1 (PC-1) or polycystin-2 (PC-2). PC-1 undergoes multiple cleavages that intervene in several signaling pathways involved in cellular proliferation and differentiation mechanisms. One of these cleavages releases the cytoplasmic C-terminal tail of PC-1. In addition, the C-terminal cytoplasmic tails of PC-1 and PC-2 interact in vitro and in vivo. The purpose of this review is to summarize recent literature that suggests that PC-1 and PC-2 may function through a common signaling pathway necessary for normal tubulogenesis. We hope that a better understanding of PC-1 and PC-2 protein function will lead to progress in diagnosis and treatment for ADPKD.
Subject(s)
Polycystic Kidney, Autosomal Dominant/metabolism , TRPP Cation Channels/metabolism , Animals , Apoptosis/physiology , Calcium Channels/metabolism , Cell Nucleus/metabolism , Cell Proliferation , Cyclic AMP/metabolism , Humans , Kidney Tubules/metabolism , Mutation , Polycystic Kidney, Autosomal Dominant/geneticsABSTRACT
Autosomal dominant polycystic kidney disease (ADPKD), a most common genetic cause of chronic renal failure, is characterized by the progressive development and enlargement of cysts in kidneys and other organs. The cystogenic process is highly complex and involves a high proliferative rate, increased apoptosis, altered protein sorting, changed secretory characteristics, and disorganization of the extracellular matrix. ADPKD is caused by mutations in the genes encoding polycystin-1 (PC-1) or polycystin-2 (PC-2). PC-1 undergoes multiple cleavages that intervene in several signaling pathways involved in cellular proliferation and differentiation mechanisms. One of these cleavages releases the cytoplasmic C-terminal tail of PC-1. In addition, the C-terminal cytoplasmic tails of PC-1 and PC-2 interact in vitro and in vivo. The purpose of this review is to summarize recent literature that suggests that PC-1 and PC-2 may function through a common signaling pathway necessary for normal tubulogenesis. We hope that a better understanding of PC-1 and PC-2 protein function will lead to progress in diagnosis and treatment for ADPKD.
La poliquistosis renal autosómica dominante (ADPKD por sus siglas en inglés) es una causa genética muy común de falla renal crónica que se caracteriza por el progresivo desarrollo y agrandamiento de quistes en los riñones y en otros órganos. El proceso de cistogénesis comprende incrementos en la proliferación y muerte celular por apoptosis, así como alteraciones en la distribución intracelular de proteínas, el movimiento transcelular de solutos y organización de la matriz extracelular. ADPKD es causada por mutaciones en los genes que codifican para policistina-1 (PC-1) o policistina-2 (PC-2). PC-1 puede sufrir múltiples clivajes y los fragmentos generados intervienen en diferentes cascadas de señalización involucradas en mecanismos de proliferación y diferenciación celular. Uno de estos clivajes libera el extremo C-terminal citoplasmático de la PC-1. Se ha demostrado que los extremos C-terminal citoplasmático de PC-1 y PC-2 pueden interactuar tanto in vitro como in vivo. El propósito de esta revisión es resumir la literatura más reciente que sugiere que PC-1 y PC-2 pueden funcionar a través de una cascada de señalización común necesaria para la tubulogénesis normal. Creemos que una mejor comprensión de los mecanismos moleculares de acción de PC-1 y PC-2 contribuirán al progreso en el diagnóstico y tratamiento de ADPKD.
Subject(s)
Animals , Humans , Polycystic Kidney, Autosomal Dominant/metabolism , TRPP Cation Channels/metabolism , Apoptosis/physiology , Cell Proliferation , Calcium Channels/metabolism , Cell Nucleus/metabolism , Cyclic AMP/metabolism , Kidney Tubules/metabolism , Mutation , Polycystic Kidney, Autosomal Dominant/geneticsABSTRACT
Autosomal dominant polycystic kidney disease (ADPKD), a most common genetic cause of chronic renal failure, is characterized by the progressive development and enlargement of cysts in kidneys and other organs. The cystogenic process is highly complex and involves a high proliferative rate, increased apoptosis, altered protein sorting, changed secretory characteristics, and disorganization of the extracellular matrix. ADPKD is caused by mutations in the genes encoding polycystin-1 (PC-1) or polycystin-2 (PC-2). PC-1 undergoes multiple cleavages that intervene in several signaling pathways involved in cellular proliferation and differentiation mechanisms. One of these cleavages releases the cytoplasmic C-terminal tail of PC-1. In addition, the C-terminal cytoplasmic tails of PC-1 and PC-2 interact in vitro and in vivo. The purpose of this review is to summarize recent literature that suggests that PC-1 and PC-2 may function through a common signaling pathway necessary for normal tubulogenesis. We hope that a better understanding of PC-1 and PC-2 protein function will lead to progress in diagnosis and treatment for ADPKD.(AU)
La poliquistosis renal autosómica dominante (ADPKD por sus siglas en inglés) es una causa genética muy común de falla renal crónica que se caracteriza por el progresivo desarrollo y agrandamiento de quistes en los riñones y en otros órganos. El proceso de cistogénesis comprende incrementos en la proliferación y muerte celular por apoptosis, así como alteraciones en la distribución intracelular de proteínas, el movimiento transcelular de solutos y organización de la matriz extracelular. ADPKD es causada por mutaciones en los genes que codifican para policistina-1 (PC-1) o policistina-2 (PC-2). PC-1 puede sufrir múltiples clivajes y los fragmentos generados intervienen en diferentes cascadas de señalización involucradas en mecanismos de proliferación y diferenciación celular. Uno de estos clivajes libera el extremo C-terminal citoplasmático de la PC-1. Se ha demostrado que los extremos C-terminal citoplasmático de PC-1 y PC-2 pueden interactuar tanto in vitro como in vivo. El propósito de esta revisión es resumir la literatura más reciente que sugiere que PC-1 y PC-2 pueden funcionar a través de una cascada de señalización común necesaria para la tubulogénesis normal. Creemos que una mejor comprensión de los mecanismos moleculares de acción de PC-1 y PC-2 contribuirán al progreso en el diagnóstico y tratamiento de ADPKD.(AU)
Subject(s)
Animals , Humans , Polycystic Kidney, Autosomal Dominant/metabolism , TRPP Cation Channels/metabolism , Apoptosis/physiology , Calcium Channels/metabolism , Cell Nucleus/metabolism , Cell Proliferation , Cyclic AMP/metabolism , Kidney Tubules/metabolism , Mutation , Polycystic Kidney, Autosomal Dominant/geneticsABSTRACT
Autosomal dominant polycystic kidney disease (ADPKD) is one of the most common human life-threatening monogenic disorders. The disease is characterized by bilateral, progressive renal cystogenesis and cyst and kidney enlargement, often leading to end-stage renal disease, and may include extrarenal manifestations. ADPKD is caused by mutation in one of two genes, PKD1 and PKD2, which encode polycystin-1 (PC1) and polycystin-2 (PC2), respectively. PC2 is a non-selective cation channel permeable to Ca2+, while PC1 is thought to function as a membrane receptor. The cyst cell phenotype includes increased proliferation and apoptosis, dedifferentiation, defective planar polarity, and a secretory pattern associated with extracellular matrix remodeling. The two-hit model for cyst formation has been recently extended by the demonstration that early gene inactivation leads to rapid and diffuse development of renal cysts, while inactivation in adult life is followed by focal and late cyst formation. Renal ischemia/reperfusion, however, can function as a third hit, triggering rapid cyst development in kidneys with Pkd1 inactivation induced in adult life. The PC1-PC2 complex behaves as a sensor in the primary cilium, mediating signal transduction via Ca2+ signaling. The intracellular Ca2+ homeostasis is impaired in ADPKD, being apparently responsible for the cAMP accumulation and abnormal cell proliferative response to cAMP. Activated mammalian target for rapamycin (mTOR) and cell cycle dysregulation are also significant features of PKD. Based on the identification of pathways altered in PKD, a large number of preclinical studies have been performed and are underway, providing a basis for clinical trials in ADPKD and helping the design of future trials.