Analysis of the subcellular distribution of avian p95-APP2, an ARF-GAP orthologous to mammalian paxillin kinase linker.

We describe here the identification and characterization of avian p95-APP2, a multi-domain protein of a recently identified family of ADP-ribosylation factor (ARF)-GTPase-activating proteins (GAPs) including mammalian G protein-coupled receptor kinases (GRK)-interactor 1 (GIT1), paxillin kinase linker (PKL), and GIT2, as well as avian p95-APP1. The p95-APP2 is eluted from Rac-GTP-gamma-S, but not from Rac-GDP-beta-S columns. As other members of the family, p95-APP2 has binding regions for the focal adhesion protein paxillin, and for the Rac exchanging factor PIX.

Identification of a novel function for 67-kDa laminin receptor: increase in laminin degradation rate and release of motility fragments.

The 67-kDa laminin receptor (67LR) is a high-affinity laminin-binding protein that is overexpressed on the tumor cell surface in a variety of cancers. We report here that the 67LR molecule also functions in the proteolytic cleavage of laminin-1, a relevant event in basement membrane degradation and tumor dissemination. In the presence of a synthetic peptide (peptide G) corresponding to the 67LR laminin binding site, the rate of laminin-1 degradation by the cysteine proteinase cathepsin B was significantly increased, and a new proteolytic fragment particularly active in in vitro cell migration assays was generated.