REQUIREMENTS FOR THE CYTOPLASMIC DOMAIN OF THE ALPHA(PS1), ALPHA(PS2)AND BETA(PS) INTEGRIN SUBUNITS DURING DROSOPHILA DEVELOPMENT

The integrins are a family of transmembrane heterodimeric proteins tha t mediate adhesive interactions and participate in signaling across th e plasma membrane, In this study we examine the functional significanc e of the cytoplasmic domains of the alpha(PS1), alpha(PS2) and beta(PS ) subunits of the Drosophila Position Specific (PS) integrin family by analyzing the relationship between cytoplasmic domain structure and f unction in the context of a developing organism,By examining the abili ty of beta(PS) molecules lacking the cytoplasmic domain to rescue embr yonic abnormalities associated with PS integrin loss, we find that alt hough many embryonic events require the beta(PS) cytoplasmic domain, t his portion of the molecule is not required for at least two processes requiring PS integrins: formation of midgut constrictions and maintai ning germband integrity, Furthermore, our studies demonstrate that mut ant proteins affecting four highly conserved amino acid residues in th e cytoplasmic tail function with different efficiencies during embryon ic development, suggesting that interaction of PS integrins with cytop lasmic ligands is developmentally modulated during embryogenesis. We h ave also examined the ability of alpha(PS1) and alpha(PS2) to function without their cytoplasmic domains, By analyzing the ability of transg enes producing truncated alpha(PS) molecules to rescue abnormalities a ssociated with integrin loss, we find that the cytoplasmic tail of alp ha(PS2) is essential for both embryonic and postembryonic processes, w hile this portion of alpha(PS1) is not required for function in the wi ng and in the retina. Furthermore, temperature-shift experiments sugge st roles for the alpha(PS2) cytoplasmic domain in signaling events occ urring in the developing wing.