Parvin-ILK: An intimate relationship.

Integrin-linked kinase (ILK), PINCH and Parvin proteins form the IPP-complex that has been established as a core component of the integrin-actin link. Our recent genetic studies on Drosophila parvin, reveal that loss of function mutant defects phenocopy those observed upon loss of ILK or PINCH in the muscle and the wing, strengthening the notion that these proteins function together in the organism. Our work identified that ILK is necessary and sufficient for parvin subcellular localization, corroborating previous data indicating a direct association between these two proteins. Further genetic epistasis analysis of the IPP-complex assembly at integrin adhesion sites reveals that depending on the cell context each component is required differently. At the muscle attachment sites of the embryo, ILK is placed upstream in the hierarchy of genetic interactions required for the IPP-complex assembly. By contrast, in the wing epithelium the three proteins are mutually interdependent. Finally, we uncovered a novel property for the CH1-domain of parvin: its recruitment at the integrin-containing junctions in an ILK-dependent manner. Apparently, this ability of the CH1-domain is controlled by the inter-CH linker region. Thus, an intramolecular interaction within parvin could serve as a putative regulatory mechanism controlling the ILK-Parvin interaction.