fig7: Hypothetical working model of LPA-induced A431 colony dispersal. We hypothesize that LPA induces Ln-332 expression via TGF-β1 pathway. In our working model, LPA binds to LPA receptors on the A431 cell surface and transactivates TGF-β1 type I receptor (TGFβR1), which phosphorylates receptor-regulated Smad (R-Smad), Smad2, and Smad3. These results are supported by other previous findings [36, 40, 41]. Another potential pathway may lead to the direct induction of phosphorylation of Smad2/3.Phosphorylated Smad2/3 forms complex with Smad4 and translocates into the nucleus [41]. Smad4 functions as a positive transcriptional regulator of Ln-332 [42]. Finally, LPA enhances Ln-332 expression to promote A431 colony dispersal.

Mentions: In summary, we propose a working model of LPA-induced A431 colony dispersal (Figure 7). We hypothesize that LPA induces Ln-332 expression via the TGF-β1 pathway. In our working model, LPA binds to LPA receptors on the A431 cell surface and transactivates TGF-β1 type I receptor (TGFβR1), which phosphorylates receptor-regulated Smad (R-Smad), Smad2, and Smad3 [36]. In addition, LPA potentially induces the direct phosphorylation of Smad2/3 via LPA receptors, or LPA-induced TGF-β1 signals activate phosphorylation of Smad2/3.

Yamashita H, Tripathi M, Jourquin J, Kam Y, Liu S, Weidow B, Quaranta V - J Oncol (2010)

Bottom Line: Interestingly, these results revealed that LPA treatment upregulates several TGF-β1 target genes, including laminin-332 (Ln-332) components (α3, β3, and γ2 chains).Further, the addition of anti-Ln-332 antibody prevented LPA-treated A431 colonies from dispersing.Taken together, our results suggest that LPA-induced Ln-332 plays a significant role in migration of individual cells from A431 colonies.

Affiliation: Department of Cancer Biology, Vanderbilt University Medical Center, Nashville, TN 37232, USA.

Abstract: Lysophosphatidic acid (LPA) is a bioactive phospholipid that affects various biological functions, such as cell proliferation, migration, survival, wound healing, and tumor invasion through LPA receptors. Previously, we reported that LPA induces A431 colony dispersal, accompanied by disruption of cell-cell contacts and cell migration. However, it remains unclear how LPA affects cell migration and gene expression during A431 colony dispersal. In this paper, we performed cDNA microarray analysis to investigate this question by comparing gene expression between untreated and LPA-treated A431 cells. Interestingly, these results revealed that LPA treatment upregulates several TGF-β1 target genes, including laminin-332 (Ln-332) components (α3, β3, and γ2 chains). Western blot analysis also showed that LPA increased phosphorylation of Smad2, an event that is carried out by TGF-β1 interactions. Among the genes upregulated, we further addressed the role of Ln-332. Real-time PCR analysis confirmed the transcriptional upregulation of all α3, β3, and γ2 chains of Ln-332 by LPA, corresponding to the protein level increases revealed by western blot. Further, the addition of anti-Ln-332 antibody prevented LPA-treated A431 colonies from dispersing. Taken together, our results suggest that LPA-induced Ln-332 plays a significant role in migration of individual cells from A431 colonies.