Differences in regulation of Drosophila and vertebrate integrin affinity by talin.
Integrin-mediated cell adhesion is essential for development of multicellular organisms. In worms, flies, and vertebrates, talin forms a physical link between integrin cytoplasmic domains and the actin cytoskeleton. Loss of either integrins or talin leads to similar phenotypes. In vertebrates, talin is also a key regulator of integrin affinity. We used a ligand-mimetic Fab fragment, TWOW-1, to assess talin's role in regulating Drosophila alphaPS2 betaPS affinity. Depletion of cellular metabolic energy reduced TWOW-1 binding, suggesting alphaPS2 betaPS affinity is an active process as it is for vertebrate integrins. In contrast to vertebrate integrins, neither talin knockdown by RNA interference nor talin head overexpression had a significant effect on TWOW-1 binding. Furthermore, replacement of the transmembrane or talin-binding cytoplasmic domains of alphaPS2 betaPS with those of human alphaIIb beta3 failed to enable talin regulation of TWOW-1 binding. However, substitution of the extracellular and transmembrane domains of alphaPS2 betaPS with those of alphaIIb beta3 resulted in a constitutively active integrin whose affinity was reduced by talin knockdown. Furthermore, wild-type alphaIIb beta3 was activated by overexpression of Drosophila talin head domain. Thus, despite evolutionary conservation of talin's integrin/cytoskeleton linkage function, talin is not sufficient to regulate Drosophila alphaPS2 betaPS affinity because of structural features inherent in the alphaPS2 betaPS extracellular and/or transmembrane domains.
Helsten
Teresa L
TL
Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA. thelsten@ucsd.edu
Bunch
Thomas A
TA
Kato
Hisashi
H
Yamanouchi
Jun
J
Choi
Sharon H
SH
Jannuzi
Alison L
AL
Féral
Chloe C
CC
Ginsberg
Mark H
MH
Brower
Danny L
DL
Shattil
Sanford J
SJ
D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D003593:Cytoplasm / Q000378:metabolism; D004330:Drosophila / Q000378:metabolism*; D005434:Flow Cytometry; D005786:Gene Expression Regulation; D016023:Integrins / Q000378:metabolism*; D008954:Models, Biological; D010641:Phenotype; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D034622:RNA Interference; D016608:Talin / Q000737:chemistry*
D016023:Integrins; D016608:Talin