ASAP3 is a focal adhesion-associated Arf GAP that functions in cell migration and invasion.

Laboratory of Cellular and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
Journal of Biological Chemistry (Impact Factor: 4.57). 06/2008; 283(22):14915-26. DOI: 10.1074/jbc.M709717200
Source: PubMed

ABSTRACT ASAP3, an Arf GTPase-activating protein previously called DDEFL1 and ACAP4, has been implicated in the pathogenesis of hepatocellular carcinoma. We have examined in vitro and in vivo functions of ASAP3 and compared it to the related Arf GAP ASAP1 that has also been implicated in oncogenesis. ASAP3 was biochemically similar to ASAP1: the pleckstrin homology domain affected function of the catalytic domain by more than 100-fold; catalysis was stimulated by phosphatidylinositol 4,5-bisphosphate; and Arf1, Arf5, and Arf6 were used as substrates in vitro. Like ASAP1, ASAP3 associated with focal adhesions and circular dorsal ruffles. Different than ASAP1, ASAP3 did not localize to invadopodia or podosomes. Cells, derived from a mammary carcinoma and from a glioblastoma, with reduced ASAP3 expression had fewer actin stress fiber, reduced levels of phosphomyosin, and migrated more slowly than control cells. Reducing ASAP3 expression also slowed invasion of mammary carcinoma cells. In contrast, reduction of ASAP1 expression had no effect on migration or invasion. We propose that ASAP3 functions nonredundantly with ASAP1 to control cell movement and may have a role in cancer cell invasion. In comparing ASAP1 and ASAP3, we also found that invadopodia are dispensable for the invasive behavior of cells derived from a mammary carcinoma.

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    • "These kinases were chosen because (1) their endogenous activity can be both induced and inhibited pharmacologically and (2) the phosphorylation of their substrates can be readily detected using commercially available antibodies. For instance, in the first round of validation experiments, we observed that DDEFL1/ASAP3, a GTPase activating protein involved in cell differentiation and migration (Ha et al, 2008), underwent a PKC-dependent increase in its protein levels (Figure 2B, top panel). "
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    • "In addition to PH and Arf GAP domains, ASAP1 contains an N-terminal Bin, Amphiphysin, and Rvs167/Rvs161 (BAR) domain and, in the C-terminal half of the protein, a proline (Pro)-rich domain and Src homology 3 (SH3) domain. Other ASAP isoforms, ASAP2 and ASAP3, have similar domain structures and high homology, especially in the Arf GAP domains, although ASAP3 lacks C-terminal SH3 domain (Ha et al., 2008). Through its Pro-rich and SH3 domains, ASAP1 interacts with a number of proteins, which are mainly adhesion-and actin cytoskeleton–related proteins including Src, focal adhesion kinase (FAK), Crk/CrkL, and cortactin (Brown et al., 1998; Liu et al., 2002; Oda et al., 2003; Onodera et al., 2005; Bharti et al., 2007). "
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