The IQGAP-myosin light chain interaction: what is its function?

The first members of the IQGAP family of proteins were<br/>characterised over 15 years ago. It is now known that these molecules act<br/>at the interface between cellular signalling pathways and the actin<br/>cytoskeleton. They bind to a diverse range of signalling molecules –<br/>including those involved in calcium, GTPase, kinase and growth factor<br/>signalling. One intriguing interaction is that between mammalian<br/>IQGAP1 and the myosin essential light chain isoform, Mlc1sa. Although<br/>this has been demonstrated in vitro, its in vivo role is not known. Indeed,<br/>it would be tempting to dismiss it as an experimental artefact, except for<br/>the existence of a parallel interaction in the budding yeast,<br/>Saccharomyces cerevisae. In this organism, the IQGAP-like protein<br/>(Iqg1p) interacts with a myosin essential light chain (Mlc1p). This interaction is critical for the correct execution of cytokinesis. IQGAP-like<br/>proteins also play key roles in cytokinesis in other fungi. Recent work<br/>implicating mammalian IQGAP1 in cytokinesis may help explain the role<br/>of the interaction in higher eukarytotes.