PI3K-AKT, JAK2-STAT3 pathways and cell–cell contact regulate maspin subcellular localization

Abstract

Background Maspin (SERPINB5) is a potential tumor suppressor gene with pleiotropic biological activities, including regulation of cell proliferation, death, adhesion, migration and gene expression. Several studies indicate that nuclear localization is essential for maspin tumor suppression activity. We have previously shown that the EGFR activation leads to maspin nuclear localization in MCF-10A cells. The present study investigated which EGFR downstream signaling molecules are involved in maspin nuclear localization and explored a possible role of cell–cell contact in this process. Methods MCF-10A cells were treated with pharmacological inhibitors against EGFR downstream pathways followed by EGF treatment. Maspin subcellular localization was determined by immunofluorescence. Proteomic and interactome analyses were conducted to identify maspin-binding proteins in EGF-treated cells only. To investigate the role of cell–cell contact these cells were either treated with chelating agents or plated on different cell densities. Maspin and E-cadherin subcellular localization was determined by immunofluorescence. Results We found that PI3K-Akt and JAK2-STAT3, but not MAP kinase pathway, regulate EGF-induced maspin nuclear accumulation in MCF-10A cells. We observed that maspin is predominantly nuclear in sparse cell culture, but it is redistributed to the cytoplasm in confluent cells even in the presence of EGF. Proteomic and interactome results suggest a role of maspin on post-transcriptional and translation regulation, protein folding and cell–cell adhesion. Conclusions Maspin nuclear accumulation is determined by an interplay between EGFR (via PI3K-Akt and JAK2-STAT3 pathways) and cell–cell contact.

The implications of alternative pre-mRNA splicing in cell signal transduction

“…Signal transduction can exert a synergistic effect while reinforcing signaling mediated through crosstalk among pathways. Examples include the effect of STAT3 activation on the Ras and PI3K/Akt pathways and the connections of JAK2 with the PI3K and ERK pathways [155][156][157][158][159][160] . Thus, the effects of splice variants may be broader than those identified in a single pathway.…”

P176S Mutation Rewires Electrostatic Interactions That Alter Maspin Functionality

“…Furthermore, maspin cellular localization is regulated by cellular confluency and epidermal growth factor receptor-related pathways, implicating their role in maspin function. 62 Nuclear-localized maspin inhibits breast cancer proliferation. 13 Similarly, Dzinic et al reported that nuclearlocalized maspin effectively inhibits HDAC1 functions and suppresses the growth of multiple cancer cell lines, including lung and prostate, and that nuclear localization is favored by mutations around the RCL region (maspin-D346E).…”

“…In our analysis, maspin-S176 was slightly more exposed (Figure S4A,B), which should favor nuclear localization; however, for antitumor activity, more than one variable may be involved. Furthermore, maspin cellular localization is regulated by cellular confluency and epidermal growth factor receptor-related pathways, implicating their role in maspin function . Nuclear-localized maspin inhibits breast cancer proliferation .…”

P176S polymorphism in Maspin rewires electrostatic interaction that alters Maspin functionality

“…4A & B) that should favor nuclear localization, however, for antitumor activity, there may be more than one variable involved. Further, maspin cellular localization is regulated by cellular confluency and epidermal growth factor receptor-related pathways implicating their role in maspin functions (Longhi et al ., 2021). Nuclear localized maspin has been reported to inhibit breast cancer proliferation (Tanaka et al ., 2020).…”