A Novel Signal Transduction Cascade Involving Direct Physical Interaction of the Renin/Prorenin Receptor With the Transcription Factor Promyelocytic Zinc Finger Protein

Abstract

Abstract-A human renin/prorenin receptor (RER) has recently been cloned. To gain insight into the molecular function of the RER, we studied its signal transduction mechanisms. Initially, we found a ubiquitous and intracellular expression pattern of the human RER. Consistently, we observed several transcriptional start sites and a high promoter activity of the human RER. We could identify the transcription factor promyelocytic zinc finger (PLZF) protein as a direct protein interaction partner of the C-terminal domain of the RER by yeast 2-hybrid screening and coimmunoprecipitation. Coimmunoprecipitation experiments also indicated homodimerization of the RER. On activation of the RER by renin, PLZF is translocated into the nucleus and represses transcription of the RER itself, thereby creating a very short negative feedback loop, but activates transcription of the p85␣ subunit of the phosphatidylinositol-3 kinase (PI3K-p85␣). Small interfering RNA against the RER abolished these effects. A PLZF cis-element in the RER promoter was identified by site-directed mutagenesis and electrophoretic mobility-shift assay. Renin stimulation caused a 6-fold recruitment of PLZF to this promoter region as shown by chromatin immunoprecipitation. Moreover, renin stimulation of rat H9c2 cardiomyoblasts induced an increase of cell number and a decrease of apoptosis. These effects were partly abolished by PI3K inhibition and completely abrogated by small interfering RNA against PLZF. Finally, experiments in PLZF knockout mice confirmed the role of PLZF as an upstream regulator of RER and PI3K-p85␣. Our data demonstrate the existence of a novel signal transduction pathway involving the ligand renin, RER, and the transcription factor PLZF, which is of physiological and putative pathophysiological relevance. Key Words: renin receptor Ⅲ PLZF Ⅲ ChIP Ⅲ signal transduction R enin and prorenin are classically thought of as (pro)enzymes of the renin/angiotensin system (RAS), but recent evidence suggests that they also act as hormones because of their ability to bind cellular targets. 1 In 2002 a human renin/prorenin receptor (RER) has been cloned, which consists of 350 amino acids with a single transmembrane domain and specifically binds prorenin and renin. Interestingly, this receptor exerts a dual molecular function 2,3 (1) Binding of renin to its receptor increases the catalytic activity of renin approximately 4-to 5-fold. Furthermore, prorenin, which does not exhibit significant ability to generate angiotensin I in solution, gains enzymatic activity comparable to renin by binding to the RER, ie, the receptor is able to unmask the catalytic activity of prorenin. (2) The RER is also able to induce a signal transduction cascade on ligand binding. Binding of renin and also prorenin causes phosphorylation of the receptor and activation of the mitogen-activated protein kinases ERK 1 and 2 (extracellular signal-regulated kinases 1 and 2), whereas intracellular calcium or cAMP levels are not altered. Remarkably, even deglycosylated renin is able t...

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“…A major amount of the receptor is located on intracellular vesicles, whereas only a fraction is found on the plasma membrane. 91,108 In contrast, a predominance of (P)RR expression was noted at the luminal surface of rat kidney collecting duct intercalated cells. 102 The full-length (P)RR, after trafficking to the Golgi, is cleaved by protease furin to liberate a 28 kDa fragment called soluble (P)RR and the 8.9 kDa fragment.…”

“…Similarly, in transgenic animals, where circulating prorenin was 200 times more than renin failed to cause cardiac or kidney fibrosis but were hypertensive, and the increase in blood pressure could be antagonized by Ang-converting enzyme inhibitors. 105,106 The discrepancy in the effect of HRP, and the absence of an end-organ damage in pregnancy and transgenic animals are probably because of: (a) decreased expression of cathepsin enzyme in kidneys of diabetic rats, 107 (b) absence of non-proteolytic activation of prorenin because of downregulation of (P)RR via activation of the transcription factor promyelocytic zinc-finger pathway, 108 (c) subcellular localization and intracellular processing of (P)RRs and their association with v-H + -ATPase, 107,109 (d) the varying affinity of the molecular forms of (P)RRs for (pro)renin 109 and (e) the difference in distribution of full-length receptor to soluble receptor 107 in a disease condition. A recent report suggests that angiotensinogen is cleaved differently by free renin and renin bound to (P)RR.…”

“…113 The v-H + -ATPase is a multisubunit complex molecule that is organized into the V 1 (eight subunits) and V O (six subunits) sectors and two accessory subunits (Ac45 and (P)RR/ATP6ap2) localized mainly within intracellular compartments and to a minor part at the plasma membrane. 91,108,112 The (P)RR/ATP6AP2 senses the acidity levels of the intracellular compartments and accordingly regulates v-H + -ATPase activity. 112 The disruption of pH homeostasis in v-H + -ATPase mutants showed lethality in various organisms.…”

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“…27 Renin also activates the (pro)renin receptor, which triggers several mitogen-activated protein kinase signaling pathways. [16][17][18] Altogether, through both angiotensin-dependent and -independent roles, renin has an important role in the regulation of BP and in the development of hypertension, atherosclerosis, cardiac remodeling and heart failure. 28 These previous reports suggest that polymorphisms in the PCSK1 gene may be involved in the development of hypertension in humans.…”

“…14 PCSK1 is also involved in the proteolytic processing of prorenin to renin, this phenomenon has been demonstrated in cells containing secretory granules, such as the somatomammotroph cell line GH4 and Chinese hamster ovary' cells. 15 Renin is important in the reninangiotensin-aldosterone system (RAAS) and may regulate vasoconstriction and BP via angiotensin-dependent and -independent mechanisms, [16][17][18] thereby facilitating hypertension, cardiac remodeling and microvascular damage.…”