Functional analysis of parvin and different modes of IPP-complex assembly at integrin sites during Drosophila development

Abstract

SummaryIntegrin-linked kinase (ILK), PINCH and parvin constitute the tripartite IPP complex that maintains the integrin-actin link at embryonic muscle attachment sites (MASs) in Drosophila. Here we showed that parvin null mutants in Drosophila exhibit defects in muscle adhesion, similar to ILK and PINCH mutants. Furthermore, the identical muscle phenotype of the triple mutant, which for the first time in any organism removed the entire IPP-complex function, genetically demonstrated that parvin, ILK and PINCH function synergistically. This is consistent with the tight localization of the tripartite complex at sites of integrin adhesion, namely MASs in the developing embryo and focal-contact-like structures in the wing epithelium. Parvin contains tandem unconventional calponin-homology (CH) domains separated by a linker sequence, and a less-well conserved N-terminal region. In vivo structure-function analysis revealed that all the domains are essential for parvin function, whereas recruitment at integrin adhesion sites is mediated by two localization signals: one located within the CH2 domain as previously reported, and a second novel signal within the CH1 domain. Interestingly, this site is masked by the linker region between the two CH domains, suggesting a regulatory mechanism to control parvin localization. Finally, whereas in muscles only ILK controls the stability and localization of both PINCH and parvin, in the wing epithelium the three proteins mutually depend on each other. Thus molecular differences exist in the assembly properties of IPP complex in specific tissues during development, where differential modulation of the integrin connection to the cytoskeleton is required.

IPP Complex Reinforces Adhesion by Relaying Tension-Dependent Signals to Inhibit Integrin Turnover

“…To determine if integrin adhesion requires the IPP-complex function, we analyzed the spatiotemporal distribution of b PS integrin and F-actin at MASs in wild-type and Ilk mutant embryos when muscle contractility gets elevated in late-stage embryogenesis. Loss of ILK destabilizes parvin and PINCH proteins, abolishing their recruitment to the MAS and signifying a loss of IPP-complex function (Vakaloglou et al, 2012;Zervas et al, 2011). At 16.5 hr of embryo development, IPP-complex mutants and wild-type embryos were identical with regard to muscle adhesion, b PS -GFP expression, and tight localization at MASs ( Figure S1; Table S1).…”

“…In addition, IPP complex facilitates stable linkage between integrins and F-actin later in embryogenesis (Clark et al, 2003;Vakaloglou et al, 2012;Zervas et al, 2001).…”

“…In mice, the IPP complex regulates cellular contractility, F-actin polarization, microtubule organization, and dynamics (Akhtar and Streuli, 2013;Kogata et al, 2009;Montanez et al, 2009;Sakai et al, 2003), whereas in Drosophila, the IPP complex maintains integrin-actin linkage (Clark et al, 2003;Vakaloglou et al, 2012;Zervas et al, 2001).…”

A dual role for integrin‐linked kinase and β1‐integrin in modulating cardiac aging

“…Cardiac-specific driver hand- Gal4 and cardiomyocyte-specific driver GMH5 have been previously described (Wessells et al ., 2004; Han & Olson, 2005). parvin 694 (Vakaloglou et al ., 2012), stck T2 (Zervas et al ., 2011), and rhea 79A (Brown et al ., 2002) were kindly provided by C. Zervas.…”

Identification of Novel Elements of the Drosophila Blisterome Sheds Light on Potential Pathological Mechanisms of Several Human Diseases

“…Delta is a ligand activating the developmentally important Notch signaling cascade [18], the blistery protein product (human orthologue – tensin) has an actin binding function and acts as an adaptor stabilizing integrin adhesive contacts in Drosophila [19], while inflated encodes the αPS2 integrin subunit [3], [8]. Another overlap with previously published data is parvin , implicated in the integrin adhesion in Drosophila [20] and mammals [21]. However, the majority of the genes (see Table S2) have never been previously implicated in wing blistering.…”