INTERACTION OF DROSOPHILA INHIBITORS OF APOPTOSIS WITH THICK VEINS, ATYPE-I SERINE THREONINE KINASE RECEPTOR FOR DECAPENTAPLEGIC/

Decapentaplegic (Dpp) is a Drosophila member of bone morphogenetic pro teins, which belong to the transforming growth factor-beta superfamily . Members of this family regulate a variety of biological processes su ch as cell proliferation, morphogenesis, immune response, and apoptosi s. Dpp plays a critical role in many aspects of Drosophila development . Members of the transforming growth factor-beta superfamily bind to t wo different types of serine/threonine kinase receptors, termed type I and type II. Type I receptors act as downstream components of type II receptors in the receptor complexes. Therefore, intracellular protein s that interact with the type I receptors are likely to play important roles in signaling. Several proteins have been identified through pro tein-protein interaction screenings. We identified Drosophila inhibito r of apoptosis (DIAP) 1 as an interacting protein of a Dpp type I rece ptor, Thick veins (Tkv). DIAP1 associates with Tkv in vivo. The bindin g region in DIAP1 is mapped to its C-terminal RING finger region. DIAP 2, another Drosophila member of the inhibitor of apoptosis protein fam ily, also interacts with Tkv in vivo. These data suggest that DIAP1 an d DIAP2 may be involved, possibly as negative regulators, in the Dpp s ignaling pathway, which leads to cell apoptosis.