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Disruption of C-terminal cytoplasmic domain of betaPS integrin subunit has dominant negative properties in developing
Alison L Jannuzi1, Thomas A Bunch, Marc C Brabant
1Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ 85721, USA.
Abstract:
We have analyzed a set of new and existing strong mutations in the myospheroid gene, which encodes the betaPS 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 (alphaPS2) 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 betaPS. The third antimorphic mutation is caused by a stop codon just before the cytoplasmic splice site. These mutant betaPS 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 beta 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 beta subunit cytoplasmic mutations.
Insights
Mutations in the Drosophila myospheroid gene can cause dominant negative effects. Disrupting the betaPS integrin cytoplasmic domain leads to antimorphic alleles with significant consequences.
Area of Science:
- Developmental Biology
- Cell Biology
- Genetics
Background:
- Integrins are crucial cell surface receptors involved in cell adhesion and signaling.
- The betaPS integrin subunit, encoded by the myospheroid gene in Drosophila, plays a vital role in development.
- Understanding mutation effects is key to deciphering protein function and cellular mechanisms.
Purpose of the Study:
- To analyze novel and existing strong mutations in the Drosophila myospheroid gene.
- To characterize the dominant negative properties of specific betaPS integrin mutations.
- To investigate the mechanisms underlying these dominant negative effects in vivo and in vitro.
Main Methods:
- Genetic analysis of Drosophila myospheroid mutations, including complementation tests.
- Characterization of antimorphic alleles and their synthetic lethality with other mutations.
- Biochemical and cellular assays to assess mutant protein function and expression.
Main Results:
- Identified three antimorphic alleles of the myospheroid gene, exhibiting dominant negative properties.
- These antimorphic mutants showed synthetic lethality with the alphaPS2 integrin null allele.
- Mutations affecting the C-terminal cytoplasmic domain of betaPS integrin can cause dominant negative effects.
- Mutant betaPS proteins supported cell spreading in culture, suggesting complex functional interactions.
Conclusions:
- Disruptions in the C-terminal cytoplasmic domain of integrin beta subunits can exert dominant negative effects.
- These effects occur at normal expression levels and do not necessarily require altered protein sequences.
- The findings provide insights into integrin function and the impact of specific mutations, with relevance to vertebrate systems.
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