Vol. 13, Issue 4, 1352-1365, April 2002

Disruption of C-Terminal Cytoplasmic Domain of PS Integrin Subunit Has Dominant Negative Properties in Developing Drosophila

Alison L. Jannuzi, Thomas A. Bunch, Marc C. Brabant, Steven W. Miller, Leona Mukai, Michael Zavortink, and Danny L. Brower^*

Department of Molecular and Cellular Biology and Department of Biochemistry, University of Arizona, Tucson, Arizona 85721

We have analyzed a set of new and existing strong mutations in the myospheroid gene, which encodes the PS integrin subunit of Drosophila. In addition to missense and other null mutations, three mutants behave as antimorphic alleles, indicative of dominant negative properties. Unlike null alleles, the three antimorphic mutants are synthetically lethal in double heterozygotes with an inflated (PS2) null allele, and they fail to complement very weak, otherwise viable alleles of myospheroid. Two of the antimorphs result from identical splice site lesions, which create a frameshift in the C-terminal half of the cytoplasmic domain of PS. The third antimorphic mutation is caused by a stop codon just before the cytoplasmic splice site. These mutant PS proteins can support cell spreading in culture, especially under conditions that appear to promote integrin activation. Analyses of developing animals indicate that the dominant negative properties are not a result of inefficient surface expression, or simple competition between functional and nonfunctional proteins. These data indicate that mutations disrupting the C-terminal cytoplasmic domain of integrin  subunits can have dominant negative effects in situ, at normal levels of expression, and that this property does not necessarily depend on a specific new protein sequence or structure. The results are discussed with respect to similar vertebrate  subunit cytoplasmic mutations.