| Summary: | The distintegrin-like and metalloproteinase with thrombospondin repeats (ADAMTS) are members of a gene family of secreted, multidomain and multifunctional proteinases that are able to proteolytically degrade a diverse array of cellular, extracellular and extracellular matrix (ECM) substrates. We examined the presence of ADAMTS in first trimester human placenta and only ADAMTS-12 was present in cultures of invasive extravillous cytotrophoblast (EVT) at significantly higher levels than in poorly invasive JEG-3 chorocarcinoma cells. Immunohistochemistry staining of chorionic villi derived from first trimester human placenta demonstrated that ADAMTS-12 was intensively immunolocalized in the cytotrophoblast layer but weakly immunolocalized in the poorly-invasive syncytial trophoblast layer. Gonadotropin-releasing hormone (GnRH)-I and -II increased ADAMTS-12 expression in EVT in time- and concentration-dependent manners, and these two hormones exert functions through different pathways.
Loss- or gain-of function studies using siRNA and stable transfection strategies demonstrated that the ADAMTS-12 promotes trophoblast invasion. Surprisingly, this function of ADAMTS-12 is independent of its catalytic activity. C-terminal sequential deletions of ADAMTS-12 demonstrated that the disintegrin-like domain plays crucial role in cellular localization of ADAMTS-12.
Laminin-5 is a component of the ECM, influencing cell migration and adhesion. The disintegrin-like domain and ancillary domains of ADAMTS-12 are associated with increased laminin-5 expression in JEG-3 cells through the activation of the ERK/MAPK signaling pathway. The integrin expression repertoire is also modified by ADAMTS-12. In particular, laminin-5 receptor integrin α6β4 is increased by the exogenous expression of ADAMTS-12 in JEG-3 cells.
Together, these data support a novel hypothesis that ADAMTS-12 plays a non-redundant role in human trophoblastic cell invasion, which is independent of its catalytic activity but dependent on the disintegrin-like domain and ancillary domains. This role involves alteration of cell-ECM interactions, which leads to a reduction of cell adhesion capability and promotes cell invasion.
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