Identification of a novel splice variant of human PD-L1 mRNA encoding an isoform-lacking Igv-like domain.
OBJECTIVE
To investigate the expression and regulation of PD-1 ligand 1 (PD-L1) in peripheral blood mononuclear cells (PBMC).


METHODS
The cDNA encoding human PD-L1 precursor was cloned from the total RNA extracted from the resting and phorbol dibutyrate plus ionomycin- or phytohemagglutinin-activated PBMC, by reverse transcription polymerase chain reaction (RT-PCR), and independent clones were sequenced and analyzed. The expression and subcellular localization were examined in transiently transfected cells. The PD-L1 gene expression in different PBMC was also analyzed by RT-PCR.


RESULTS
A novel human PD-L1 splice variant was identified from the activated PBMC. It was generated by splicing out exon? encoding an immunoglobulin variable domain (Igv)-like domain but retaining all other exons without a frame-shift. Consequently, the putative translated protein contained all other domains including the transmembrane region except for the Igv-like domain. Furthermore, the conventional isoform was expressed on the plasma surface whereas the novel isoform showed a pattern of intracellular membrane distribution in transiently transfected K562 cells. In addition, the expression pattern of the PD-L1 splice variant was variable in different individuals and in different cellular status.


CONCLUSIONS
PD-L1 expression may be regulated at the posttranscriptional level through alternative splicing, and modulation of the PD-L1 isoform expression may influence the outcome of specific immune responses in the peripheral tissues.
He
Xian-hui
XH
Key Laboratory of Ministry of Education for Tissue Transplantation and Immunology, Ji-nan University, Guangzhou 510632, China. thexh@jnu.edu.cn
Xu
Li-hui
LH
Liu
Yi
Y
D000328:Adult; D017398:Alternative Splicing; D000595:Amino Acid Sequence; D015703:Antigens, CD; D018122:B7-1 Antigen / Q000096:biosynthesis / Q000235:genetics*; D060890:B7-H1 Antigen; D001483:Base Sequence; D003001:Cloning, Molecular; D005091:Exons; D014644:Genetic Variation; D006801:Humans; D007135:Immunoglobulin Variable Region / Q000235:genetics*; D007536:Isomerism; D020014:K562 Cells; D007963:Leukocytes, Mononuclear / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000096:biosynthesis / Q000235:genetics*; D008969:Molecular Sequence Data; D010455:Peptides / Q000235:genetics*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D017422:Sequence Analysis, DNA; D014162:Transfection
D015703:Antigens, CD; D018122:B7-1 Antigen; D060890:B7-H1 Antigen; C423236:CD274 protein, human; D007135:Immunoglobulin Variable Region; D008562:Membrane Glycoproteins; D010455:Peptides; D012333:RNA, Messenger