Lipid Rafts and Cytoskeletal Proteins in Placental Microvilli Membranes from Preeclamptic and IUGR Pregnancies

Abstract

Intrauterine growth restriction (IUGR) and preeclampsia (PE) are leading causes of perinatal and maternal morbidity and mortality. Previously we reported the expression of lipid rafts in classical microvillous membrane (MVM) and light microvillous membrane (LMVM), two subdomains in apical membrane from the human placental syncytiotrophoblast (hSTB), which constitute the epithelium responsible for maternal-fetal transport. Here the aim was to study the raft and cytoskeletal proteins from PE and IUGR. Microdomains from MVM and LMVM were tested with raft markers (placental alkaline phosphatase, lipid ganglioside, and annexin 2) and a nonraft marker (hTf-R). No changes were detected with those markers in whole purified apical membranes in normal, PE, and IUGR pregnancies; however, their patterns of distribution in lipid rafts were different in PE and IUGR. Cholesterol depletion modified their segregation, confirming their presence in lipid rafts, although unlike normal placenta, in these pathologies there is only one type of microdomain. Additionally, the cytoskeleton proteins actin, ezrin, and cytokeratin-7 showed clear differences between normal and pathological membranes. Cytokeratin-7 expression decreased to 50% in PE, and the distribution between LMVM and MVM (~43 and 57%, respectively) changed in both PE and IUGR, in contrast with the asymmetrical enrichment obtained in normal LMVM (~62%). In conclusion, lipid rafts from IUGR and PE have different features compared to rafts from normal placentae, and this is associated with alterations in the expression and distribution of cytoskeletal proteins.

Differential Expression of Potassium Channels in Placentas from Normal and Pathological Pregnancies: Targeting of the Kir 2.1 Channel to Lipid Rafts

“…Channels in Domains and Subdomains from Placental hSTB Apical (MVM, LMVM) and basal membranes (BM) from NP and from PE and IUGR placentas were isolated and purified using the protocol described in ''Materials and Methods'' section. We found similar enrichment markers and cross-membrane contamination markers as described fully in previous work (Jimenez et al 2004;Riquelme et al 2011). We purified the membranes from 11 NPs, 4 PE placentas, and 5 IUGR placentas.…”

“…However, there was a difference between MVM and LMVM, which are the two subdomains from apical membranes, in that K v 2.1 expression was 26 ± 8% in the LMVM and 59 ± 9% in the MVM. In previous reports (see brief review in Riquelme 2011), we suggested that the two subdomains from the apical hSTB membranes were correlated: MVM corresponded to the microvillous finger-like region of the apical subdomain, and LMVM corresponded to the apical subdomain that constituted the base of the finger-like projections (Godoy and Riquelme 2008;Riquelme et al 2011;Riquelme 2011). Then, we determined that most of the K v was located in the microvillous finger-like region.…”

“…They were tested for the presence of specific raft and nonraft markers as described in Godoy and Riquelme (2008) and Riquelme et al (2011). We confirmed the quality of our preparations using immunoblotting.…”

“…As we described in Godoy and Riquelme (2008) and Riquelme et al (2011), normal placenta (NP)/PE/IUGR DRMs from isolated apical fractions (MVM and LMVM) were extracted with 1% Triton X-100 on ice and subjected to ultracentrifugation and sucrose flotation. After centrifugation, the gradients were divided into 10 fractions (0.5 ml each) from the top of the gradient and the pellet was resuspended in 0.5 ml MBS-buffered saline (25 mM morpholinoethanesulfonic acid, 150 mM NaCl, pH 6.5; fraction 11) for subsequent analysis.…”

“…These membrane microdomains are characterized by their resistance to detergent extraction and their ability to float in density gradient centrifugation (Godoy and Riquelme 2008;Riquelme 2011). The domains, subdomains, and microdomains were also characterized in placentas from pregnancy pathology, including preeclampsia (PE) and intrauterine growth restriction (IUGR) (Jimenez et al 2004;Riquelme et al 2011). PE is a hypertensive disease associated with proteinuria, sometimes with edemas (Lindheimer and Katz 1989), and affects up to 6% of all gestations beyond 20 weeks, especially in primiparous women.…”