Deficiency of miR-409-3p improves myocardial neovascularization and function through modulation of DNAJB9/p38 MAPK signaling.

Angiogenesis is critical for tissue repair following myocardial infarction (MI), which is exacerbated under insulin resistance or diabetes. MicroRNAs are regulators of angiogenesis. We examined the metabolic regulation of miR-409-3p in post-infarct angiogenesis. miR-409-3p was increased in patients with acute coronary syndrome (ACS) and in a mouse model of acute MI. In endothelial cells (ECs), miR-409-3p was induced by palmitate, while vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF) decreased its expression. Overexpression of miR-409-3p decreased EC proliferation and migration in the presence of palmitate, whereas inhibition had the opposite effects. RNA sequencing (RNA-seq) profiling in ECs identified DNAJ homolog subfamily B member 9 (DNAJB9) as a target of miR-409-3p. Overexpression of miR-409-3p decreased DNAJB9 mRNA and protein expression by 47% and 31% respectively, while enriching DNAJB9 mRNA by 1.9-fold after Argonaute2 microribonucleoprotein immunoprecipitation. These effects were mediated through p38 mitogen-activated protein kinase (MAPK). Ischemia-reperfusion (I/R) injury in EC-specific miR-409-3p knockout (KO) mice (miR-409ECKO) fed a high-fat, high-sucrose diet increased isolectin B4 (53.3%), CD31 (56%), and DNAJB9 (41.5%). The left ventricular ejection fraction (EF) was improved by 28%, and the infarct area was decreased by 33.8% in miR-409ECKO compared with control mice. These findings support an important role of miR-409-3p in the angiogenic EC response to myocardial ischemia.

CDC2 Is an Important Driver of Vascular Smooth Muscle Cell Proliferation via FOXM1 and PLK1 in Pulmonary Arterial Hypertension.

A key feature of pulmonary arterial hypertension (PAH) is the hyperplastic proliferation exhibited by the vascular smooth muscle cells from patients (HPASMC). The growth inducers FOXM1 and PLK1 are highly upregulated in these cells. The mechanism by which these two proteins direct aberrant growth in these cells is not clear. Herein, we identify cyclin-dependent kinase 1 (CDK1), also termed cell division cycle protein 2 (CDC2), as having a primary role in promoting progress of the cell cycle leading to proliferation in HPASMC. HPASMC obtained from PAH patients and pulmonary arteries from Sugen/hypoxia rats were investigated for their expression of CDC2. Protein levels of CDC2 were much higher in PAH than in cells from normal donors. Knocking down FOXM1 or PLK1 protein expression with siRNA or pharmacological inhibitors lowered the cellular expression of CDC2 considerably. However, knockdown of CDC2 with siRNA or inhibiting its activity with RO-3306 did not reduce the protein expression of FOXM1 or PLK1. Expression of CDC2 and FOXM1 reached its maximum at G1/S, while PLK1 reached its maximum at G2/M phase of the cell cycle. The expression of other CDKs such as CDK2, CDK4, CDK6, CDK7, and CDK9 did not change in PAH HPASMC. Moreover, inhibition via Wee1 inhibitor adavosertib or siRNAs targeting Wee1, Myt1, CDC25A, CDC25B, or CDC25C led to dramatic decreases in CDC2 protein expression. Lastly, we found CDC2 expression at the RNA and protein level to be upregulated in pulmonary arteries during disease progression Sugen/hypoxia rats. In sum, our present results illustrate that the increased expression of FOXM1 and PLK1 in PAH leads directly to increased expression of CDC2 resulting in potentiated growth hyperactivity of PASMC from patients with pulmonary hypertension. Our results further suggest that the regulation of CDC2, or associated regulatory proteins, will prove beneficial in the treatment of this disease.

Identification of LTR-specific small non-coding RNA in FeLV infected cells.

The U3-LTR region of leukemia viruses transactivates cancer-related signaling pathways through the production of a non-coding RNA transcript although the role of this transcript in virus infection remains unknown. In this study we demonstrate for the first time that an long terminal repeat (LTR)-specific small non-coding RNA is produced from a feline leukemia virus (FeLV)-infected feline cell line. RNA cloning identified this as a 104 base transcript that originates from the U3-LTR region. We also demonstrate that in in vitro assays this LTR-RNA transcript activates NF kappaB signaling. Taken together, our findings suggest a possible role for this LTR transcript in FeLV pathogenesis.

Chimeric exchanges within the bradykinin B2 receptor intracellular face with the prostaglandin EP2 receptor as the donor: importance of the second intracellular loop for cAMP synthesis.

The prostaglandin E2 (PGE(2)) EP2 receptor (EP2R) type is G protein coupled (GPCR) and links to Galphas. Through this receptor PGE(2) activates cAMP production. The bradykinin (BK) B2 receptor (BKB2R) is also a GPCR but links to Galphaq and Galphai and does not activate cAMP production in response to bradykinin. In an attempt to convert the BKB2R into a Galphas-linked adenylate cyclase-activating receptor we proceeded to make global and discrete motif replacements of the intracellular (IC) face of the BKB2R with the corresponding regions of the human EP2R. With this approach we produced hybrid receptors which, when stably transfected into wild type (WT) Rat-1 cells, bound BK but produced cAMP. Replacement of the second loop (IC2), third loop (IC3), the entire C terminus, and the distal C terminus resulted in receptors which bound BK. However, only the IC2 and IC3 exchanges resulted in cAMP-producing receptors. Of these two regions, the IC2 exchange was by far the better cAMP-generating receptor, producing cAMP at approximately 6.6-fold above WT BKB2R or approximately one fourth the amount produced by WT EP2R-transfected Rat-1 cells. Both human and rat EP2R and human beta2-adrenergic receptor exchanges of the IC2 produced equal quantities of cAMP. Focusing on the rBKB2R/hEP2R IC2 chimeras, the region consisting of residues 136-147 (BKB2R residue numbering) proved to contain a cAMP-generating motif. Within this region, the proximal six amino acids from the EP2R (HPYFYQ) at position 136-141 proved crucial for cAMP production (10-fold over WT BKB2R). The distal part of this region, the six residues at 142-147, played no role in cAMP production. On the other hand, the ALV motif of the BKB2R IC2, residues 133-135, proved important with respect to phosphatydilinositol (PI) turnover. Replacing the entire IC2 of BKB2R resulted in poor PI turnover, while including the AVL of BKB2R retained approximately half of the WT PI turnover. With respect to receptor uptake, all the IC2 mutants endocytosed as WT BKB2R (60% in 1h). However, the exchange of the distal and the whole C termini resulted in a marked drop in endocytosis (30% in 1h). These results demonstrate that the construction of a cAMP-producing BKB2/EP2 receptor hybrid is possible, with the IC2 region distal to DRYLALV proving important to Galphas linkage and the LALV motif within the IC2 of BKB2R and the region proximal to it proving important for Galphaq and Galphai linkage. Additionally, our results confirm the importance of the distal C terminus in determining receptor uptake.

Hybrid formation between the intracellular faces of the bradykinin B2 and angiotensin II AT1 receptors and signal transduction.

Most frequently, the physiologic functions of the angiotensin II (Ang II) type 1 receptor (AT1R) and bradykinin B2 receptor (BKB2R) are antagonistic, particularly with respect to the regulation of vascular tone. Despite major differences in their physiologic actions, the receptors share sequence similarities. Both link to Galpha(i) and Galpha(q) and transduce very similar signal paths, not only those relating to the traditional G-protein associated second messengers, but also those involved in transactivation mechanisms involving receptor tyrosine kinases. With respect to these paths, some differences in signaling may be accounted for by cell type specificity. However, alternative signal cascades for these two receptors are becoming increasingly evident. One such is the recruitment of signaling molecules upon receptor translocation and internalization. The AT1R translocates into clathrin-coated pits and internalizes upon recruitment of beta-arrestin 2 which then recruits ASK1 and JNK3. The BKB2R translocates and internalizes mainly via caveolae. Another signaling divergence may be due to the direct activation of small G-proteins by both receptors. AT1R activates the RhoA, Rac1, Cdc42 while BKB2R couples only with Rac1 and Cdc42. Both receptors may serve as docking stations for intracellular proteins. One such example is the YIPP motif within the C-terminus of the ATIR which associates with the JAK/STAT pathway. Another potential alternative is the activation of tyrosine/serine kinase phosphatases by BK. This mechanism may directly oppose some of the protein tyrosine/ serine kinase paths activated by AT1R. These alternative mechanisms in sum are potentially responsible for the diversion in signal transduction between these two receptors. Regardless of the route of action, our results suggest that in Rat-1 fibroblasts stably transfected with BKB2R, BK slightly decreases connective tissue growth factor (CTGF) mRNA level while in ATIR transfected cells Ang II increases CTGF mRNA markedly. To determine whether mutant hybrids can be formed between these two receptors which encompass some of the function of the donor receptor but bind the ligand of the recipient receptor, a series of hybrids were formed with BKB2R the recipient and AT1R the donor receptor. Some of these hybrids show resistance to exchanges with the AT1R and form receptors which either do not bind (IC1 exchanges) or demonstrate poor function but normal internalization (proximal C-terminus exchanges). However, other hybrids have proven very functional. For example, the IC2, IC3 and distal C-terminus of the BKB2R IC face can be replaced simultaneously with the AT1R resulting in an hybrid which binds BK, continues to signal, is internalized and resensitized. Formation of this and other less extensive hybrids is discussed. Some of these hybrids possess the capacity to function as the AT1R as exemplified by their ability to upregulate CTGF expression as wild-type (WT) AT1R.