MUPP-1 (multi-PDZ domain protein-1) and PATJ (PALS-1-associated tight junction protein) proteins are closely related scaffold proteins and bind to many common interactors including PALS-1 (protein ass Show more
MUPP-1 (multi-PDZ domain protein-1) and PATJ (PALS-1-associated tight junction protein) proteins are closely related scaffold proteins and bind to many common interactors including PALS-1 (protein associated with Lin seven) a member of the Crumbs complex. Our goal is to understand how MUPP-1 and PATJ and their interaction with PALS-1 are regulated in the same cells. We have shown that in MCF10A cells there are at least two different and co-existing complexes, PALS-1/MUPP-1 and PALS-1/PATJ. Surprisingly, MUPP-1 levels inversely correlated with PATJ protein levels by acting on the stabilization of the PATJ/PALS-1 complex. Upon MUPP-1 depletion, the increased amounts of PATJ are in part localized at the migrating front of MCF10A cells and are able to recruit more PAR3 (partition defective 3). All together these data indicate that a precise balance between MUPP-1 and PATJ is achieved in epithelial cells by regulating their association with PALS-1. Show less
The formation of functional epithelial tissues involves the coordinated action of several protein complexes, which together produce a cell polarity axis and develop cell-cell junctions. During the las Show more
The formation of functional epithelial tissues involves the coordinated action of several protein complexes, which together produce a cell polarity axis and develop cell-cell junctions. During the last decade, the notion of polarity complexes emerged as the result of genetic studies in which a set of genes was discovered first in Caenorhabditis elegans and then in Drosophila melanogaster. In epithelial cells, these complexes are responsible for the development of the apico-basal axis and for the construction and maintenance of apical junctions. In this review, we focus on apical polarity complexes, namely the PAR3/PAR6/aPKC complex and the CRUMBS/PALS1/PATJ complex, which are conserved between species and along with a lateral complex, the SCRIBBLE/DLG/LGL complex, are crucial to the formation of apical junctions such as tight junctions in mammalian epithelial cells. The exact mechanisms underlying their tight junction construction and maintenance activities are poorly understood, and it is proposed to focus in this review on establishing how these apical polarity complexes might regulate epithelial cell morphogenesis and functions. In particular, we will present the latest findings on how these complexes regulate epithelial homeostasis. Show less