Heterogeneous nuclear ribonucleoprotein A1 is a novel cellular target of atrial natriuretic peptide signaling in renal epithelial cells

Abstract

Two classes of guanylyl cyclases (GC) form intracellular cGMP. One is a receptor for atrial natriuretic peptide (ANP) and the other for nitric oxide (NO). The ANP receptor guanylyl cyclase (GC-A) is a membrane-bound, single subunit protein. Nitric oxide activated or soluble guanylyl cyclases (NOGC) are heme-containing heterodimers. These have been shown to be important in cGMP mediated regulation of arterial vascular resistance and renal sodium transport. Recent studies have shown that cGMP produced by both GCs is compartmentalized in the heart and vascular smooth muscle cells. To date, however, how intra cellular cGMP generated by ANP and NO is compartmentalized and how it triggers specific downstream targets in kidney cells has not been investigated. Our studies show that intracellular cGMP formed by NO is targeted to cytosolic and cytoskeletal compartments whereas cGMP formed by ANP is restricted to nuclear and membrane compartments. We used two dimensional Difference in Gel Electrophoresis and MALDI-TOF/TOF to identify distinct sub-cellular targets that are specific to ANP and NO signaling in HK-2 cells. A nucleocytoplasmic shuttling protein, heterogeneous nuclear ribonucleo protein A1 (hnRNP A1) is preferentially phosphorylated by ANP/cGMP/cGK signaling. ANP stimulation of HK-2 cells leads to increased cGK activity in the nucleus and translocation of cGK and hnRNP A1 to the nucleus. Phosphodiestaerase-5 (PDE-5 inhibitor) sildenafil augmented ANP–mediated effects on hnRNPA1 phosphorylation, translocation to nucleus and nuclear cGK activity. Our results suggest that cGMP generated by ANP and SNAP is differentially compartmentalized, localized but not global changes in cGMP, perhaps at different sub-cellular fractions of the cell, may more closely correlate with their effects by preferential phosphorylation of cellular targets.

The dipeptidyl peptidase inhibitor linagliptin and the angiotensin II receptor blocker telmisartan show renal benefit by different pathways in rats with 5/6 nephrectomy

“…35 HNRNPA1 phosphorylation plays a major role in the downstream nuclear signaling of atrial natriuretic peptide through cyclic guanosine monophosphate and cyclic guanosine monophosphate-dependent protein kinase. 36 In the kidney, a disturbance of atrial natriuretic peptide-mediated cyclic guanosine monophosphate synthesis is known to be a trigger of fibrosis. 36 Thus, an activation of the atrial natriuretic peptidedependent guanylate cyclase pathway may contribute to the antifibrotic properties of linagliptin.…”

“…36 In the kidney, a disturbance of atrial natriuretic peptide-mediated cyclic guanosine monophosphate synthesis is known to be a trigger of fibrosis. 36 Thus, an activation of the atrial natriuretic peptidedependent guanylate cyclase pathway may contribute to the antifibrotic properties of linagliptin. 37,38 Based on our current data, which is derived from a candidate-pathway approach in combination with an open approach, and our current understanding of the mode of action of DPP-4 inhibitors, 10 we conclude that the pharmacological effects of linagliptin cannot be explained by interacting with a single pathway.…”

Triiodothyronine Potentiates Vasorelaxation via PKG/VASP Signaling in Vascular Smooth Muscle Cells

“…In some experiments, cells were pre-treated with 2 µM of KT5823, a selective PKG inhibitor from Sigma Aldrich (St.Louis, MO, US), for 30 minutes. The concentration of KT5823 utilized in this study was chosen based on published reports [26, 27]. To investigate whether T3 alters PKG mRNA and protein expression, quiescent human aortic VSMC were treated with T3 for 24 hours.…”

Depletion of cyclic‐GMP levels and inhibition of cGMP‐dependent protein kinase activate p21 Cip1 /p27 Kip1 pathways and lead to renal fibrosis and dysfunction

“…The CycLex cGK assay uses a peroxidase coupled anti‐phospho‐G kinase substrate monoclonal antibody reporter molecule. The assay system provides a non‐radioactive, sensitive, and specific method to measure the cGK activity 58 …”

“…The assay system provides a non-radioactive, sensitive, and specific method to measure the cGK activity. 58…”