OBJECTIVE: The di-leucine motif exists in the intracellular domains of certain cell surface receptors, participating in the receptor-mediated endocytosis. The present study was aimed at determining the role of the di-leucine motif in class A scavenger receptor (SR-A)-mediated ligand endocytosis. METHODS AND RESULTS: cDNA coding for a mutant (SR-A mutant N3132LM) with deletion of the di-leucine structure was transfected into Chinese hamster ovary (CHO) cells. Compared with wild-type SR-A-expressing cells, the cells expressing the SR-A mutant N3132LM showed a significant decrease in uptake but almost no change in binding of the SR-A ligand acetylated low-density lipoprotein (AcLDL). Western blot analysis revealed coimmunoprecipitation of SR-A mutant and clathrin from the lysates of the mutant but not wild-type CHO cells, suggesting that AcLDL-bound SR-A mutant N3132LM is associated with the clathrin-coated pit of cellular membrane. Removal of the first 27 amino acid residues from the SR-A N-terminus further reduced AcLDL uptake by the cells with the di-leucine motif mutation. CONCLUSIONS: The di-leucine motif of SR-A intracellular domain contributes to the SR-A-mediated cellular internalization of AcLDL. Di-leucine pair exists in the cytoplasmic domain of class A scavenger receptor. The cells expressing di-leucine mutants showed decreased uptake and unchanged binding of AcLDL. The di-leucine pair was not associated to coated pits. It suggests that di-leucine motif acts as a signal sequence to mediate SR-A into cell.
OBJECTIVE: The di-leucine motif exists in the intracellular domains of certain cell surface receptors, participating in the receptor-mediated endocytosis. The present study was aimed at determining the role of the di-leucine motif in class A scavenger receptor (SR-A)-mediated ligand endocytosis. METHODS AND RESULTS: cDNA coding for a mutant (SR-A mutant N3132LM) with deletion of the di-leucine structure was transfected into Chinese hamster ovary (CHO) cells. Compared with wild-type SR-A-expressing cells, the cells expressing the SR-A mutant N3132LM showed a significant decrease in uptake but almost no change in binding of the SR-A ligand acetylated low-density lipoprotein (AcLDL). Western blot analysis revealed coimmunoprecipitation of SR-A mutant and clathrin from the lysates of the mutant but not wild-type CHO cells, suggesting that AcLDL-bound SR-A mutant N3132LM is associated with the clathrin-coated pit of cellular membrane. Removal of the first 27 amino acid residues from the SR-A N-terminus further reduced AcLDL uptake by the cells with the di-leucine motif mutation. CONCLUSIONS: The di-leucine motif of SR-A intracellular domain contributes to the SR-A-mediated cellular internalization of AcLDL. Di-leucine pair exists in the cytoplasmic domain of class A scavenger receptor. The cells expressing di-leucine mutants showed decreased uptake and unchanged binding of AcLDL. The di-leucine pair was not associated to coated pits. It suggests that di-leucine motif acts as a signal sequence to mediate SR-A into cell.
Authors: Sam L Stephen; Katie Freestone; Sarah Dunn; Michael W Twigg; Shervanthi Homer-Vanniasinkam; John H Walker; Stephen B Wheatcroft; Sreenivasan Ponnambalam Journal: Int J Hypertens Date: 2010-08-17 Impact factor: 2.420
Authors: Izma Abdul Zani; Sam L Stephen; Nadeem A Mughal; David Russell; Shervanthi Homer-Vanniasinkam; Stephen B Wheatcroft; Sreenivasan Ponnambalam Journal: Cells Date: 2015-05-22 Impact factor: 6.600