Identification of cysteine-rich epidermal growth factor-like domain 1α (CRELD1 α) as a novel α1A-adrenoceptor-down-regulating protein and establishment of an α1L-adrenoceptor-expressing cell line

Two distinct α1-adrenoceptor phenotypes (α1a- and α1l-ars) are known to originate from a single adra1a(α1a) gene by an as-yet-unknown mechanism. we hypothesized that an α1a-ar-interacting protein could generate the α1l-ar phenotype and we sought to identify such a protein and to examine its effects on the expression of α1a and α1l phenotypes. cysteine-rich epidermal growth factor-like domain 1α (creld1α) was first identified using a yeast two-hybrid approach as an α1a-ar-interacting protein. transfection of α1a-ar cdna alone yielded chinese hamster ovary (cho) cells expressing α1a-ars having a predominant high affinity site for prazosin,with a low proportion (<10%) of prazosin-low affinity sites (α1l-ar). knockdown of endogenous cho-creld1α [α1a-ckd(α1a-enhanced) cells] enhanced the expression of α1a-ar,whereas over-expression of creld1α reduced α1a-ar expression,yielding α1a-coe(α1l-dominant) cells expressing a high proportion (50%) of the α1l-ar phenotype. the ligand binding and functional agonist and antagonist profiles in α1a-ckd(α1a-enhanced) and α1a-coe(α1l-dominant) cell lines were entirely in accord with the α1a-ar and α1l-ar phenotypes observed in intact tissues. creld1α down-regulates expression of the α1a-ar,thereby enhancing the proportion of expression of the α1l-ar phenotype. the α1l-ar-expressing α1a-coe(α1l-dominant) cell line reflects accurately the phenotype of this ar observed in vivo and will facilitate development of α1l-ar-targeted drugs. © 2010 the japanese pharmacological society.