Principal expression of two mRNA isoforms (ABCB 5alpha and ABCB 5beta ) of the ATP-binding cassette transporter gene ABCB 5 in melanoma cells and melanocytes.
ATP-binding cassette (ABC) transporters play a pivotal role in physiology and pathology. We identified and cloned two novel mRNA isoforms (ABCB 5alpha and ABCB 5beta) of the ABC transporter ABCB 5 in human melanoma cells. The deduced ABCB 5alpha protein appears to be an altered splice variant containing only a putative ABC, whereas the ABCB 5beta isoform shares approximately 70% similarity with ABCB1 (MDR1) and has a deduced topological arrangement similar to that of the whole carboxyl terminal half of the ABCB1 gene product, P-glycoprotein, including an intact ABC. Northern blot, real-time PCR, and conventional RT-PCR were used to verify the expression profiles of ABCB 5alpha/beta. We found that the melanomas included among the NCI-60 panel of cell lines preferentially expressed both ABCB 5alpha and ABCB 5beta. However, ABCB 5alpha/beta expression was undetectable in two amelanotic melanomas (M14 and LOX-IMVI). The expression profile of ABCB 5alpha/beta in all of the other melanomas of the panel was confirmed both by RT-PCR and by sequencing. Neither ABCB 5alpha nor ABCB 5beta expression was found in normal tissues such as liver, spleen, thymus, kidney, lung, colon, small intestines or placenta. ABCB 5alpha/beta mRNAs were also expressed in normal melanocytes and in retinal pigment epithelial cells, suggesting that ABCB 5alpha/beta expression is pigment cell-specific and might be involved in melanogenesis. Our findings indicate that expression of ABCB 5alpha/beta might possibly provide two novel molecular markers for differential diagnosis of melanomas and constitute potential molecular targets for therapy of melanomas.
Chen
Kevin G
KG
Laboratory of Cell Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA.
Szakács
Gergely
G
Annereau
Jean-Philippe
JP
Rouzaud
Francois
F
Liang
Xing-Jie
XJ
Valencia
Julio C
JC
Nagineni
Chandrasekharam N
CN
Hooks
John J
JJ
Hearing
Vincent J
VJ
Gottesman
Michael M
MM
D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000096:biosynthesis* / Q000235:genetics; D017398:Alternative Splicing; D000595:Amino Acid Sequence; D001483:Base Sequence; D014408:Biomarkers, Tumor / Q000096:biosynthesis / Q000235:genetics; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D018432:Drug Resistance, Multiple; D019008:Drug Resistance, Neoplasm; D020869:Gene Expression Profiling; D015723:Gene Library; D006801:Humans; D008544:Melanocytes / Q000378:metabolism*; D008545:Melanoma; D008969:Molecular Sequence Data; D009928:Organ Specificity; D012333:RNA, Messenger / Q000096:biosynthesis*
C480744:ABCB5 protein, human; D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D014408:Biomarkers, Tumor; D012333:RNA, Messenger