Comparison of Saccharomyces cerevisiae F-BAR Domain Structures Reveals a Conserved Inositol Phosphate Binding Site

Abstract

SUMMARY F-BAR domains control membrane interactions in endocytosis, cytokinesis, and cell signaling. Although generally thought to bind curved membranes containing negatively charged phospholipids, numerous functional studies argue that differences in lipid-binding selectivities of F-BAR domains are functionally important. Here, we compare membrane-binding properties of the S. cerevisiae F-BAR domains in vitro and in vivo. Whereas some F-BAR domains (such as Bzz1p and Hof1p F-BARs) bind equally well to all phospholipids, the F-BAR domain from the RhoGAP Rgd1p preferentially binds phosphoinositides. We determined X-ray crystal structures of F-BAR domains from Hof1p and Rgd1p, the latter bound to an inositol phosphate. The structures explain phospholipid-binding selectivity differences, and reveal an F-BAR phosphoinositide binding site that is fully conserved in a mammalian RhoGAP called Gmip, and is partly retained in certain other F-BAR domains. Our findings reveal previously unappreciated determinants of F-BAR domain lipid-binding specificity, and provide a basis for its prediction from sequence.

Hof1 and Chs4 Interact via F-BAR Domain and Sel1-like Repeats to Control Extracellular Matrix Deposition during Cytokinesis

“…Furthermore, we found that the F-BAR domain, not the CC2 region, of Hof1-N-term interacted directly with Chs4-SLR (Figure 1D). Hof1-F-BAR is known to form dimers and bind non-selectively to a number of phospholipids in vitro with no apparent tubulation activity in vivo [33]. …”

“…All F-BAR domains form crescent dimers that bind to negatively charged phospholipids. Unlike Hof1 in budding yeast or Cdc15 in the fission yeast S. pombe [33, 46], many F-BAR domain-containing proteins can generate membrane curvatures by forming helical filaments via lateral as well as end-to-end associations [21]. The F-BAR proteins usually link cellular membranes to the actin cytoskeleton and/or cellular signaling via other domains such as the SH3 and GTPase-activating domains (GAPs) for Rho GTPases and function in a number of cellular processes such as endocytosis, cell migration, and cytokinesis [22, 46].…”

Mechanics and regulation of cytokinesis in budding yeast

“…Inn1 contains a C2 domain at its N-terminus that is essential for PS formation, and several PXXP motifs at its C-terminus that bind to the SH3 domains of Hof1 and Cyk3 [36]. Hof1 is a F-BAR protein [32, 140-142] and Cyk3 contains a transglutaminase domain [143, 144]. These proteins interact with each other and share an essential role in AMR-independent cytokinesis [41, 137, 138, 143].…”

Linking up at the BAR: Oligomerization and F-BAR protein function

“…F-BAR domains interact with negatively charged membranes primarily through the concave face of their crescent shaped dimers, utilizing multiple positively charged surface residues. 3,8,9,15 PACSIN F-BAR domains also contain a unique amphipathic "wedge-loop" that partially inserts into the bilayer 16 ; mutations in this region consequently disrupt membrane binding. The concave orientation of membrane binding is conserved in all F-BARs, though a few variations have been proposed.…”

“…In fact, multiple F-BAR proteins do not tubulate membranes in standard in vitro liposome binding or cultured cell overexpression assays. These include: Fer, 6 Fes, RhoGAP4, Gas7, and FCHSD1/2, 9 as well as S. pombe Cdc15, 9 S. cerevisiae Hof1, 15 and Drosophila Nwk. 17 It could be argued that the perfect condition (such as a specific lipid composition) has not been discovered to support tubulation of these F-BARs.…”