Currently, the function of RAMPs is divided into classes of activities. When associated with the Calcitonin receptor (CTR) or Calcitonin receptor-like (CALCRL) (below), RAMPs can change the selectivity of the receptor for a specific hormone. In the cases of the other receptors mentioned, however, there is no evidence that they can do this, but instead function to regulate trafficking of receptors from the ER / golgi to the membrane. These functions appear to be ones where there is redundancy, as neither RAMP1 nor RAMP3 knockout mice (KO) have grossly abnormal phenotypes. The likelihood is that the phenotype of RAMP2 KO mice is more connected with the abolition of most adrenomedullin (AM) signalling than effects on trafficking of other receptors, as those mice are almost identical to AM KO mice.
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^McLatchie LM, Fraser NJ, Main MJ, Wise A, Brown J, Thompson N, Solari R, Lee MG, Foord SM (May 1998). "RAMPs regulate the transport and ligand specificity of the calcitonin-receptor-like receptor". Nature. 393 (6683): 333–9. doi:10.1038/30666. PMID9620797.
^Kamitani S, Asakawa M, Shimekake Y, Kuwasako K, Nakahara K, Sakata T (April 1999). "The RAMP2/CRLR complex is a functional adrenomedullin receptor in human endothelial and vascular smooth muscle cells". FEBS Lett. 448 (1): 111–4. doi:10.1016/S0014-5793(99)00358-0. PMID10217420.