GTPase-activating protein for ADP ribosylation factor family members, including ARF1. Multidomain scaffold protein that interacts with numerous proteins and therefore participates in many cellular functions, including receptor internalization, focal adhesion remodeling, and signaling by both G protein-coupled receptors and tyrosine kinase receptors (By similarity). Through Pak activation, may positively regulate microtubule nucleation during interphase. May play a role in the regulation of cytokinesis (By similarity). During embryogenesis, promotes proper muscle morphogenesis and proper guidance and targeting of subsets of myotubes (PubMed:18996366). Required for the recruitment of Pak to muscle attachments in the embryo, probably indirectly through pix/dPIX (PubMed:18996366). May be important for brain development (PubMed:25792865). May form homodimers (via coiled coil) (By similarity). Forms a complex with pix and Pak; the interaction with Pak may be indirect and mediated by pix/dPIX (PubMed:18996366). Localizes to the leading edge of growing myotubes. Expressed in embryonic muscle syncytia (at protein level). Detected muscle syncytia in embryonic stage 14 and early stage 15. At mid stage 15, localizes at the leading edge of growing myotubes. In the ventral ends of VO5 and VO6 muscles enriched at the base of membrane protrusions at the leading edge of growing myotubes, while it is less expressed in filopodia. In the late stage embryo, concentrated at all muscle attachment sites, although subtle variation in expression and/or localization may be observed in different muscles subsets. Remains enriched in myotubes until the end of embryogenesis (at protein level). The coiled coil region may mediate dimerization. Homozygous knockout flies show a semi-lethal phenotype and exhibit defective wing morphology at 100% penetrance (PubMed:18996366). Mutant embryos show striking guidance phenotypes in ventral oblique muscle 5 (VO5) and ventral oblique muscle 6 (VO6), characterized by bypass and mistargeting of the mutant muscles toward the ventral midline. Defects in targeting of the growing ventral tips of mutant muscles toward the ventral midline are already detectable at late stage 14/early stage 15 embryos. Defects in other ventral muscles are less obvious, although ventral acute muscle 3 (VA3) occasionally show mistargeting toward the ventral midline (PubMed:18996366). Defects in number and shape of subsets of muscles are also observed, but at low frequency (PubMed:18996366). Adult knockout flies show decreased central brain size and abnormal morphology of the mushroom body, the most common pattern being early termination of one alpha-lobe. The penetrance of the impaired mushroom body development is incomplete (PubMed:25792865).