Requirements for the cytoplasmic domain of the α(PS1), α(PS2) and β(PS) integrin subunits during Drosophila development

Abstract

The integrins are a family of transmembrane heterodimeric proteins that mediate adhesive interactions and participate in signaling across the plasma membrane. In this study we examine the functional significance of the cytoplasmic domains of the α(PS1), α(PS2) and β(PS) subunits of the Drosophila Position Specific (PS) integrin family by analyzing the relationship between cytoplasmic domain structure and function in the context of a developing organism. By examining the ability of β(PS) molecules lacking the cytoplasmic domain to rescue embryonic abnormalities associated with PS integrin loss, we find that although many embryonic events require the β(PS) cytoplasmic domain, this portion of the molecule is not required for at least two processes requiring PS integrins: formation of midgut constrictions and maintaining germband integrity. Furthermore, our studies demonstrate that mutant proteins affecting four highly conserved amino acid residues in the cytoplasmic tail function with different efficiencies during embryonic development, suggesting that interaction of PS integrins with cytoplasmic ligands is developmentally modulated during embryogenesis. We have also examined the ability of α(PS1) and α(PS2) to function without their cytoplasmic domains. By analyzing the ability of transgenes producing truncated α(PS) molecules to rescue abnormalities associated with integrin loss, we find that the cytoplasmic tail of α(PS2) is essential for both embryonic and postembryonic processes, while this portion of α(PS1) is not required for function in the wing and in the retina. Furthermore, temperature-shift experiments suggest roles for the α(PS2) cytoplasmic domain in signaling events occurring in the developing wing.