Disease relevance of RAMP3

• Recently, we also found that not only levels of AM peptide and AM gene expression, but also mRNA levels of CRLR, RAMP2 and RAMP3 are increased in cardiac hypertrophy and failing heart [1].
• The lack of upregulation of RAMP-3 during late sepsis could also contribute to the decreased clearance observed during this phase [2].

High impact information on RAMP3

• However, in the presence of NHERF-1, although the AM receptor (CRLR/RAMP3) undergoes desensitization, the internalization of the receptor complex is blocked [3].
• When examined in a primary culture of human proximal tubule cells endogenously expressing the CRLR-RAMP3 complex and NHERF-1, the CRLR-RAMP complex desensitizes but is unable to internalize upon agonist stimulation [3].
• Knock-down of either RAMP3 or NHERF-1 by RNA interference technology enabled agonist-induced internalization of the CRLR-RAMP complex [3].
• We hypothesized that a PDZ type I domain present in the C terminus of RAMP3, but not in RAMP1 or RAMP2, leads to protein-protein interactions that determine receptor trafficking [4].
• Mutational analysis of RAMP3, by deletion and point mutations, indicated that the PDZ motif of RAMP3 interacts with NSF to cause the change in trafficking [4].

Biological context of RAMP3

• The human RAMP1 and RAMP3 genes possess two introns and human RAMP2 possesses three introns [5].
• In contrast, LPS treatment markedly increased RAMP3 gene expression in lungs, spleen, and thymus [6].
• Our results showed for the first time an up-regulation of RAMP1 and RAMP3 mRNAs and proteins in this model of cardiac failure [7].
• Binding sites at area postrema appear to be composed of CTa + RAMP3 [amylin3 (a) receptors] [8].
• In contrast, a pronounced effect of RAMP C-terminal truncation was seen for RAMP/CTRa complexes, studied in COS-7 cells, with significant attenuation of amylin receptor phenotype induction that was stronger for RAMP1 and -2 than RAMP3 [9].

Anatomical context of RAMP3

• No cell line had detectable RAMP3 mRNA [10].
• Using specific oligonucleotides we have determined the expression of RAMP1, RAMP2 and RAMP3 mRNAs in the rat central nervous system by in situ hybridization [11].
• Semi-quantitative RT-PCR analysis showed that the gene expression of calcitonin receptor-like receptor and receptor-activity-modifying protein (RAMP)1, RAMP2 and RAMP3 in ventricular myocardia were up-regulated by 79% (P<0.01), 48% (P<0.01), 31% (P<0.05) and 130% (P<0.01), respectively, compared with controls [12].
• Receptor-activity-modifying protein (RAMP) 2 and RAMP3, ADM receptor subunits, are expressed in autonomic centers including the PVN and supraoptic nucleus [13].
• No significant stress-related change in RAMP3 mRAN was observed in the medulla oblongata [14].

Associations of RAMP3 with chemical compounds

• There is little sequence identity between hRAMP3 residues 59-65 and hRAMP2 residues 86-92; moreover, substituting alanine for Trp(86) (Ala(87)), Met(88), Ile(89), Ser(90), Arg(91), or Pro(92) of hRAMP2 had no effect on AM-evoked cAMP production [15].
• The equivalent residue in RAMP3, Glu74, when mutated to tryptophan (E74W), induced BIBN4096BS sensitivity at AM(2) and AMY(3(a)) receptors [16].
• RAMP3 participates in adrenomedullin (AM) binding via its extracellular N-terminus characterized by the presence of six highly conserved cysteine residues and four N-glycosylation consensus sites [17].
• METHODS: Streptozotocin (STZ)-induced diabetic Sprague-Dawley rats at 4 weeks after the injection were employed for expression studies of AM, RAPM2, and RAMP3 [18].

Physical interactions of RAMP3

• More detailed analysis showed that deletion of hRAMP2 residues 86-92 significantly attenuated high-affinity (125)I-AM binding and AM-evoked cAMP production despite full cell surface expression of the receptor heterodimer and that deletion of hRAMP3 residues 59-65 had a similar effect [15].

Other interactions of RAMP3

• Co-expression of RAMP3 together with RAMP1 reduced the maximal cAMP response to h alphaCGRP by 47% (P < 0.05) [19].
• Cells co-expressing the CL receptor and RAMP3, produced such a response, as in mammals, indicating that the human ADM molecule is not the cause of the previous unresponsiveness [20].
• These results, using both endogenous and overexpressed cellular models, indicate a novel function for NHERF-1 and RAMP3 in the internalization of the AM receptor and suggest additional regulatory mechanisms for receptor trafficking [3].
• The CGRP-selectivity of RAMP1 and RAMP3 may be conferred by a putative disulfide bond from the N-terminus to the middle of the extracellular domain of these molecules [21].
• RAMP3 is known to modify calcitonin gene-related receptor (CRLR) so that it can then serve as an ADM receptor [22].

Analytical, diagnostic and therapeutic context of RAMP3

• We have used semi-quantitative RT-PCR and Western-blot analysis to detect and quantify the mRNA and the protein of RAMP1 and RAMP3 in both atria and ventricles of failing hearts 6 months after aortic banding in rats [7].
• By Northern blot analyses, AM and RAPM2 mRNAs significantly increased in the kidneys of STZ rats, while RAMP3 mRNA was not altered [18].

References