Phospholipid Scramblase Isoform Expression in Pregnant Rat Uterus

Objective: Phospholipid scramblases (PLSCRs), a family of novel membrane proteins, facilitate the translocation of aminophospholipids from the inner to the exterior leaf of the cell membrane. Four isoforms of PLSCR (PLSCR1-4) have been reported in mouse and human. The studies described in this report sought to characterize the uterine expression of the PLSCR isoforms in the near-term pregnant rat. Methods: Uterine tissue was obtained from timed-pregnant Sprague-Dawley rats. Total RNA was isolated, treated with DNase, and used in qualitative and quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) studies utilizing PLCSR isoform PCR primers. A rat spleen cDNA bacteriophage library was used as a template for PCR-based sequencing to determine the cDNA and translated amino acid sequences for the PLSCR3 and PLSCR4 homologs expressed in rats. The 5′ and 3′ untranslated regions were obtained using 5′ and 3′ Rapid Amplification of cDNA Ends (RACE) techniques. Results: RT-PCR studies confirmed expression of PLSCR3 and PLSCR4 in the endometrial and myometrial layers of the pregnant rat uterus; in contrast, PLSCR1 and PLSCR2 were not found in uterine tissues. The cDNA sequence for the rat PLSCR3 homolog was found to be 1642 nucleotides, having 92% identity with mouse and 80% with human PLSCR3. The rat PLSCR4 homolog has a cDNA sequence of 1879 nucleotides, having an 89% identity with mouse and 72% identity with human PLSCR4 homologs. Conclusion: The intrauterine expression of PLSCR3 and PLSCR4 provides a dynamic mechanism by which aminophospholipid translocation can be regulated, thereby modulating the activity of various membrane proteins that are involved in inflammation and coagulation-related events.