PHOSPHOLIPID PHOSPHATASE 5; PLPP5

Alternative titles; symbols

• PPAP2 DOMAIN-CONTAINING PROTEIN 1B; PPAPDC1B
• HTPAP

HGNC Approved Gene Symbol: PLPP5

Cytogenetic location: 8p11.23 Genomic coordinates (GRCh38): 8:38,261,789-38,269,434 (from NCBI)

▼ Cloning and Expression
Previous studies of hepatocellular carcinoma (HCC) suggested that deletion of a region of human chromosome 8p contributes to HCC metastasis. Using cDNA microarray analysis of chromosome 8 ESTs from HCC cell lines to identify genes with downregulated expression in high metastatic potential versus low metastatic potential cell lines, followed by database analysis and RT-PCR, Wu et al. (2006) cloned PPAPDC1B, which they called HTPAP. The 175-amino acid protein contains an N-terminal transmembrane domain, an acid phosphatase homology region, 2 PKC phosphorylation sites, and a tyrosine kinase phosphorylation site. RT-PCR analysis of 16 metastatic HCC tissues paired with 16 primary HCC tissues showed downregulation of PPAPDC1B expression in 11 of 16 metastatic lesions compared to primary HCC tissues, with 9 of 16 metastatic lesions showing significant downregulation of PPAPDC1B (P less than 0.05).

▼ Gene Function
Using in vitro matrigel assays, Wu et al. (2006) showed that PPAPDC1B-transfected metastatic HCC cells showed significantly lower invasion activity. Transfection and expression of PPAPDC1B in nude mice bearing human HCC significantly decreased the incidence and degree of pulmonary metastasis of HCC.

▼ Mapping
By genomic sequence analysis, Wu et al. (2006) mapped the PLPP5 gene to chromosome 8p12.

Gross (2017) mapped the PLPP5 gene to chromosome 8p11.23 based on an alignment of the PLPP5 sequence (GenBank AF212238) with the genomic sequence (GRCh38).