Journal of Biological Chemistry
Volume 276, Issue 16, 20 April 2001, Pages 13192-13197
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LIPIDS AND LIPOPROTEINS
Identification of a Novel Exon in Apolipoprotein E Receptor 2 Leading to Alternatively Spliced mRNAs Found in Cells of the Vascular Wall but Not in Neuronal Tissue*

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Novel members of the low density lipoprotein receptor family were identified in human endothelial and vascular smooth muscle cells utilizing a homology-cloning strategy. Four novel mRNA transcripts could be identified as isoforms of the apolipoprotein E receptor 2 (apoEr2): one form lacking three ligand binding repeats (nucleotides 497–883) but containing a novel ligand binding repeat adjacent to a unique cysteine-rich domain preceding the epidermal growth factor precursor domain of apoEr2, forms lacking the O-linked sugar domain, and forms containing a 59-amino acid deletion within the cytoplasmic tail. By fluorescence in situ hybridization for chromosome mapping, we could confirm that the novel alternative forms of apoEr2 are splice variants of transcripts from a single copy gene on chromosome 1p34. To analyze whether the different splice variants of apoEr2 mRNA are expressed in a splice variant-specific pattern, we concentrated on the central nervous system, where high expression of apoEr2 has been described originally. By means of splice variant-specific in situ hybridization, we could confirm that apoEr2 mRNA is abundantly expressed in brain tissue and, with exception of the newly identified ligand binding domain, all mRNA splice variants exhibited a similar expression pattern. The mRNA of the newly identified ligand binding domain, however, was expressed in brain only in cells of the vascular wall, confirming data from Northern blotting, where the mRNA of the newly identified ligand binding domain was found in several tissues but was absent in brain tissue.

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Published, JBC Papers in Press, January 10, 2001, DOI 10.1074/jbc.M011795200

*

This work was supported in part by Austrian Science Foundation Grants F509 and P10559. An abstract of this article has been published (Korschineck, I., Ziegler, S., Breuss, J., Lang, I., Lorenz, M., Kaun, C., Ambros, P. F., and Binder, B. R. (1997)Thromb. Haemostasis 77, Suppl., p. 400, Abstr. OC1630.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The nucleotide sequence(s) reported in this paper has been submitted to the GenBank™/EMBL Data Bank with accession number(s) Z75190.

§

These authors contributed equally to this report.

1

    The abbreviations used are:

    LDLR

    low density lipoprotein receptor

    apoEr2

    apolipoprotein E receptor 2

    LRP

    LDLR-related protein

    VLDLR

    very low density lipoprotein receptor

    SMC

    smooth muscle cells

    EGF

    epidermal growth factor

    EC

    endothelial cells

    HUVEC

    human umbilical vein EC

    HSMEC

    human skin microvascular EC

    PCR

    polymerase chain reaction

    bp

    base pair(s)

    kb

    kilobase pair(s)