Relationship between novel isoforms, functionally important domains, and subcellular distribution of CD164/endolyn.
Functional analyses have indicated that the human CD164 sialomucin may play a key role in hematopoiesis by facilitating the adhesion of human CD34(+) cells to the stroma and by negatively regulating CD34(+)CD38(lo/-) cell proliferation. We have identified three novel human CD164 variants derived by alternative splicing of bona fide exons from a single genomic transcription unit. The predominant CD164(E1-6) isoform, encoded by six exons, is a type I transmembrane protein containing two extracellular mucin domains (I and II) interrupted by a cysteine-rich non-mucin domain. The 103B2/9E10 and 105A5 epitopes, which specify ligand binding characteristics, are located on the exon 1-encoded mucin domain I. Three human CD164(E1-6) mRNA species, exhibiting differential polyadenylation site usage, are differentially expressed in hematopoietic and non-hematopoietic tissues. This study provides additional evidence that human CD164(E1-6) represents the ortholog of murine MGC-24v and rat endolyn. Comparative analysis of murine MGC-24v/CD164(E1-6) with human CD164(E1-6) revealed two potential splice variants and a similar genomic structure. Whereas the human CD164 gene is located on chromosome 6q21, the mouse gene occurs in a syntenic region on chromosome 10B1-B2. By confocal microscopy, human CD164 in CD34(+)CD38(+) hematopoietic progenitor (KG1B) and epithelial cell lines appears to be localized primarily in endosomes and lysosomes, with low concentrations at the cell surface. However, in a minority of KG1B cells, CD164 is more prominently expressed at the plasma membrane and in the recycling endosomes, suggesting that its distribution is regulated in cells of hematopoietic origin.
Chan
J Y
JY
Medical Research Council Molecular Hematology Unit, Institute of Molecular Medicine, Oxford OX3 9DS, United Kingdom.
Lee-Prudhoe
J E
JE
Jorgensen
B
B
Ihrke
G
G
Doyonnas
R
R
Zannettino
A C
AC
Buckle
V J
VJ
Ward
C J
CJ
Simmons
P J
PJ
Watt
S M
SM
D000595:Amino Acid Sequence; D000818:Animals; D015703:Antigens, CD; D001483:Base Sequence; D015152:Blotting, Northern; D051929:CD146 Antigen; D002460:Cell Line; D002874:Chromosome Mapping; D018076:DNA, Complementary; D051930:Endolyn; D006801:Humans; D008562:Membrane Glycoproteins; D008969:Molecular Sequence Data; D019006:Neural Cell Adhesion Molecules; D016133:Polymerase Chain Reaction; D020033:Protein Isoforms / Q000378:metabolism*; D012326:RNA Splicing; D012333:RNA, Messenger / Q000235:genetics; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013329:Structure-Activity Relationship; D013347:Subcellular Fractions / Q000378:metabolism*
D015703:Antigens, CD; D051929:CD146 Antigen; C497898:CD164 protein, human; D018076:DNA, Complementary; D051930:Endolyn; D008562:Membrane Glycoproteins; D019006:Neural Cell Adhesion Molecules; D020033:Protein Isoforms; D012333:RNA, Messenger; D011956:Receptors, Cell Surface