Endothelial Restoration of Receptor Activity–Modifying Protein 2 Is Sufficient to Rescue Lethality, but Survivors Develop Dilated Cardiomyopathy

Abstract

Receptor activity-modifying proteins (RAMPs) serve as oligomeric modulators for numerous G protein-coupled receptors (GPCRs), yet elucidating the physiological relevance of these interactions remains complex. Receptor activity-modifying protein 2 (Ramp2) null mice are embryonic lethal, with cardiovascular developmental defects similar to those observed in mice null for canonical adrenomedullin/calcitonin receptor-like receptor (CLR) signaling. We aimed to genetically rescue the Ramp2−/− lethality in order to further delineate the spatiotemporal requirements for RAMP2 function during development and thereby enable the elucidation of an expanded repertoire of RAMP2 functions with Family B GPCRs in adult homeostasis. Endothelial-specific expression of Ramp2 under the VE-cadherin promoter resulted in the partial rescue of Ramp2−/− mice, demonstrating that endothelial expression of Ramp2 is necessary and sufficient for survival. The surviving Ramp2−/− Tg animals lived to adulthood and developed spontaneous hypotension and dilated cardiomyopathy, which was not observed in adult mice lacking CLR. Yet, the hearts of Ramp2−/− Tg animals displayed dysregulation of Family B GPCRs, including parathyroid hormone and glucagon receptors as well as their downstream signaling pathways. These data suggest a functional requirement for RAMP2 in the modulation of additional GPCR pathways in vivo, which is critical for sustained cardiovascular homeostasis. The cardiovascular importance of RAMP2 extends beyond the endothelium and canonical adrenomedullin/CLR signaling, in which future studies could elucidate novel and pharmacologically-tractable pathways for treating cardiovascular diseases.

Amylin Selectively Signals Onto POMC Neurons in the Arcuate Nucleus of the Hypothalamus

“…RAMP2 has the lowest affinity for amylin compared with RAMP1 and -3 (39,47); thus, RAMP2 might be sufficient to maintain amylin's neurotrophic effect during the neonatal period but not during adulthood, as shown by the decrease in ERK phosphorylation after amylin injection. Unfortunately, this hypothesis cannot be tested directly owing to the lethality of RAMP2 KO (48). Aside from amylin, AMY1, -2, and -3 are also the target of other peptides such as CGRP.…”

Adrenomedullin Induces Cardiac Lymphangiogenesis After Myocardial Infarction and Regulates Cardiac Edema Via Connexin 43

“…Conscious echocardiography was performed using VSI 2100 high frequency ultrasound (VisualSonics) as previously described 37 .…”

Modeling cellular crosstalk and organotypic vasculature development with human iPSC-derived endothelial cells and cardiomyocytes

“…Augmented expression of several other genes associated with heart development [30][31][32][33][34]50,51 such as SOX4, MEFC2, RAMP2, CALCRL, and APLNR and organotypic cardiac endothelial cell genes 28 , such as HAPLN1, SPRX1 and IL6ST, was observed in coculture hiPS-ECs. Many of the coculture induced genes are also known to contribute to vascular development and angiogenesis, likely reflecting their response to angiogenic factors produced by cardiomyocytes.…”

“…A gene ontology classification analysis of the 130 genes upregulated in hiPS-ECs in both cell lines revealed activation of pathways associated with cardiovascular development, cell signaling, angiogenesis, and cell differentiation ( Figure 4A). More specifically, upregulation of general EC genes ( Figure 2D), and, interestingly, cardiac EC-specific genes 28 ( Figure 4B), as well as several genes associated with heart development [29][30][31][32][33][34] (Figure 4C), and angiogenesis [35][36][37] (Figure 4D) were observed in hiPS-ECs cultured together with hiPS-CMs. The respective data for the HEL24.3 cell line are presented in Figure V in the Data Supplement.…”