The interactome of human Stanniocalcin-1 suggests new cellular functions and pathways

Author(s)

Marcos Tadeu dos Santos

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Biologia
• Defense date: 2011-08-19

Examining board members

Jörg Kobarg; Vanessa Schein; Claudio Chrysostomo Werneck; Sandra Martha Gomes Dias; Heloisa Sobreiro Selistre de Araujo

• Advisor: Jörg Kobarg

Abstract

The aims of this project is to study upregulated genes on bone marrow stromal cells, induced by the co-culture with leukemic blasts, trying to have a better understand about the crosstalk between these cells in the tumor microenvironment. We identified Stanniocalcin-1 (STC1) as a putative molecular marker for the leukemic microenvironment, once its expression was increased around 7 times in stromal cells co-cultivated with primary leukemic blasts. Human STC1 is a secreted glycoprotein that has been implicated in different physiological process, including angiogenesis, hypoxia and mainly in carcinogenesis. We produced the recombinant protein STC1 in baculovirus system and monoclonal antibodies for an ELISA assay that now will be tested as a new leukemia diagnostic kit by a Brazilian company. Moreover, we identified new interacting protein partners for STC1 by yeast two hybrid system and some of these interactions were confirmed by GST-pull down assays. The N-terminal region was mapped to be the region that mediates the interaction between STC1 and its partners. Microscopic subcellular localization, revealed an ubiquitous cytoplasmic and dot-like nuclear deposition, resembling SUMOylation related nuclear bodies. Although STC1 interacts with SUMO-1 and has a high theoretical prediction score for a SUMOylation site, in vitro and in vivo assays could not detect STC1 SUMOylation. However, we found that STC1 significantly regulates the SUMOylation of three other proteins. These ??ndings suggest a new role for STC1 in SUMOylation cycle, acting as a SUMO E3 ligase. We either observe that STC1 has a plasmatic membrane receptor in K562 leukemic cell lines and the incubation of STC1 with other leukemic cells suggest a increase of proliferation of these cells and stimulates the production of more intracellular STC1 at stromal cells. Together, all of these findings open promising new avenues to be explored in future detailed studies, since they all show interesting connections with previous functional studies on STC1 (AU)

• FAPESP's process: 07/07778-6 - Functional studies of Stanniocalcin-1, a tumor microenvironment marker, and development of an assay for its detection in the serum of leukemia patients
• Grantee: Marcos Tadeu dos Santos
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)