RESUMO

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.

Assuntos

RESUMO

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.

Assuntos

RESUMO

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)

Assuntos

RESUMO

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.

Assuntos

RESUMO

The present work was designed to study Na+ K+ ATPase alpha1-subunit phosphorylation in rats with chronic renal failure (CRF) in comparison with normal rats. Na+ K+ ATPase alpha1-subunit phosphorylation degree was measured by binding the McK-1 antibody to dephosphorylated Ser-23 in microdissected medullary thick ascending limb of Henle (mTAL) segments. In addition, the total Na+ K+ ATPase alpha1-subunit expression and activity were also measured in the outer renal medulla homogenates and membranes. CRF rats showed a higher Na+ K+ ATPase activity, as compared with control rats (18.95 +/- 2.4 vs. 11.21 +/- 1.5 micromol Pi/mg prot/h, p < 0.05), accompanied by a higher total Na+ K+ ATPase expression (0.54 +/- 0.04 vs. 0.27 +/- 0.02 normalized arbitrary units (NU), p < 0.05). When McK-1 antibody was used, a higher immunosignal in mTAL of CRF rats was observed, as compared with controls (6.3 +/- 0.35 vs. 4.1 +/- 0.33 NU, p < 0.05). The ratio Na+ K+ ATPase alpha1-subunit phosphorylation/total Na+ K+ ATPase alpha1-subunit expression per microg protein showed a non-significant difference between CRF and control rats in microdissected mTAL segments (2.11 +/- 0.12 vs. 2.26 +/- 0.18 NU, p = NS). The PKC inhibitor RO-318220 10(-6) M increased immunosignal (lower phosphorylation degree) in mTAL of CRF rats to 128.43 +/- 7.08% (p < 0.05) but did not alter McK1 binding in control rats. Both phorbol 12-myristate 13-acetate (PMA) 10(-6) M and dopamine 10(-6) M decreased immunosignal in CRF rats, corresponding to a higher Na+ K+ ATPase alpha1-subunit phosphorylation degree at Ser-23 (55.26 +/- 11.17% and 53.27 +/- 7.12% compared with basal, p < 0.05). In mTAL of CRF rats, the calcineurin inhibitor FK-506 10(-6) M did not modify phosphorylation degree at Ser-23 of Na+ K+ ATPase alpha1-subunit (100.21 +/- 3.00% compared with basal CRF). In control rats, FK 506 10(-6) M decreased the immunosignal, which corresponds to a higher Na+ K+ ATPase alpha1-subunit phosphorylation degree at Ser-23. The data suggest that the regulation of basal Na+ K+ ATPase alpha1-subunit phosphorylation degree at Ser-23 in mTAL segments of CRF rats was primarily dependent on PKC activation rather than calcineurin dependent mechanisms.

Assuntos

RESUMO

Sodium transport correlates with varying Na+-K+-ATPase activity rates along the nephron. Whether differences in Na+-K+-ATPase regulation by protein kinase C-dependent phosphorylation are also present has not been tested. We measured the degree of Na+-K+-ATPase alpha1 subunit phosphorylation by the binding of McK-1 antibody to dephosphorylated Ser-23 and Na+-K+-ATPase activity in medullary thick ascending limb of Henle (mTAL) and proximal tubules (PCT). The degree of Na+-K+-ATPase phosphorylation at Ser-23 was lower in mTAL than in PCT (DU 13.43+/-1.99 versus 2.3+/-0.20, respectively, P<0.01) while Na+-K+-ATPase activity was higher in mTAL (3,402+/-83 vs 711+/-158 pmol/mm tubule per hour in PCT, P<0.01). PKC inhibitor RO-318220 10(-6) M decreased phosphorylation in PCT to 125+/-10% ( P<0.05). In mTAL, RO-318220 did not modify the phosphorylation degree or the activity of Na+-K+-ATPase. Both calcineurin inhibitor FK-506 10(-6) M and phorbol 12-myristate 13-acetate (PMA) 10(-6) M increased the degree of Na+-K+-ATPase phosphorylation ( P<0.05) and inhibited Na+-K+-ATPase activity to 657+/-152 and 1,448+/-347 pmol/mm tubule per hour, respectively, in mTAL ( P<0.01). Increase in [Na+]i to 30, 50 and 70 mM resulted in no changes in Na+-K+-ATPase phosphorylation degree or activity in mTAL. Conversely, in PCT increments in [Na+]i were paralleled by decreased phosphorylation (from 120+/-7 to 160+/-15% of controls, P<0.05) and increased Na+-K+-ATPase activity (from 850+/-139 to 1,874+/-203 pmol/mm tubule per hour, P<0.01). Dopamine (DA) 10(-6) M decreased both Na+-K+-ATPase dephosphorylation to 41.85+/-9.58% ( P<0.05) and Na+-K+-ATPase activity to 2,405+/-176 pmol/mm tubule per hour in mTAL ( P<0.01). RO-318220 reversed DA effects. Data suggest that regulation of the degree of Na+-K+-ATPase alpha1 subunit phosphorylation at Ser-23 and enzyme activity have different mechanisms in mTAL than in PCT, and may help us to understand the physiological heterogeneity of both segments.

Assuntos

RESUMO

Previous reports have shown a stimulatory effect of vasopressin (VP) on Na-K-ATPase and rBSC-1 expression and activity. Whether these VP-dependent mechanisms are operating in vivo in physiological conditions as well as in chronic renal failure (CRF) has been less well studied. We measured ATPase expression and activity and rBSC-1 expression in the outer medulla of controls and moderate CRF rats both before and under in vivo inhibition of VP by OPC-31260, a selective V(2)-receptor antagonist. OPC-31260 decreased Na-K-ATPase activity from 11.2 +/- 1.5 to 3.7 +/- 0.8 in controls (P < 0.05) and from 19.0 +/- 0.8 to 2.9 +/- 0.5 micromol P(i). mg protein(-1) x h(-1) in moderate CRF rats (P < 0.05). CRF was associated with a significant increase in Na-K-ATPase activity (P < 0.05). Similarly, CRF was also associated with a significant increase in Na-K-ATPase expression to 164.4 +/- 21.5% compared with controls (P < 0.05), and OPC-31260 decreased Na-K-ATPase expression in both controls and CRF rats to 57.6 +/- 9.5 and 105.3 +/- 10.9%, respectively (P < 0.05). On the other hand, OPC-31260 decreased rBSC-I expression in both controls and CRF rats to 60.8 +/- 6.5 and 30.0 +/- 6.9%, respectively (P < 0.05), and was not influenced by CRF (95.7 +/- 5.2%). We conclude that 1) endogenous VP modulated Na-K-ATPase and rBSC-1 in both controls and CRF; and 2) CRF was associated with increased activity and expression of the Na-K-ATPase in the outer medulla, in contrast to the unaltered expression of the rBSC-1. The data suggest that endogenous VP could participate in the regulation of electrolyte transport at the level of the outer medulla.

Assuntos