Abstract
BackgroundCalpains are calcium regulated intracellular cysteine proteases implicated in a variety of physiological functions and pathological conditions. The Drosophila melanogaster genome contains only two genes, CalpA and CalpB coding for canonical, active calpain enzymes. The movement of the border cells in Drosophila egg chambers is a well characterized model of the eukaryotic cell migration. Using this genetically pliable model we can investigate the physiological role of calpains in cell motility.ResultsWe demonstrate at the whole organism level that CalpB is implicated in cell migration, while the structurally related CalpA paralog can not fulfill the same function. The downregulation of the CalpB gene by mutations or RNA interference results in a delayed migration of the border cells in Drosophila egg chambers. This phenotype is significantly enhanced when the focal adhesion complex genes encoding for α-PS2 integrin ( if), β-PS integrin ( mys) and talin ( rhea) are silenced. The reduction of CalpB activity diminishes the release of integrins from the rear end of the border cells. The delayed migration and the reduced integrin release phenotypes can be suppressed by expressing wild-type talin-head in the border cells but not talin-headR367A, a mutant form which is not able to bind β-PS integrin. CalpB can cleave talin in vitro, and the two proteins coimmunoprecipitate from Drosophila extracts.ConclusionsThe physiological function of CalpB in border cell motility has been demonstrated in vivo. The genetic interaction between the CalpB and the if, mys, as well as rhea genes, the involvement of active talin head-domains in the process, and the fact that CalpB and talin interact with each other collectively suggest that the limited proteolytic cleavage of talin is one of the possible mechanisms through which CalpB regulates cell migration.
Highlights
Calpains are calcium regulated intracellular cysteine proteases implicated in a variety of physiological functions and pathological conditions
When a calpain-resistant Talin1 was expressed in cells with Talin1 null background, the rate of disassembly of the focal adhesion complexes was lower indicating that adhesion turnover was regulated by the Capn2-mediated cleavage of Talin1 [7]
As we found that the downregulation of the talin-encoding gene, rhea, had a delaying effect on border cell migration, and this effect was aggravated in a CalpB505 background (Figure 3), we investigated the effects of the same conditions on integrin release
Summary
Calpains are calcium regulated intracellular cysteine proteases implicated in a variety of physiological functions and pathological conditions. Calpains are widespread and are implicated in a variety of physiological functions (signal transduction, cell motility, cell proliferation and differentiation, apoptosis, cell growth, cytoskeletal remodeling, membrane fusion) [1]. They are associated with a diverse range of. The role of calpains in the migration of Chinese Hamster Ovary (CHO) cells was demonstrated with the aid of cell-permeable calpain inhibitors and a cell line expressing reduced level of Capn1 [5] Both conditions leading to reduced calpain activity blocked cell migration at higher fibrinogen concentrations, inhibited the cell-substratum detachment at the trailing edge of the cells, and decreased the release of integrins from the cell membrane. Our knowledge about the role of individual calpains during cell migration is incomplete due to the large number and variety of calpains as well as their potential substrate proteins
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