Mechanisms and Functions of Vinculin Interactions with Phospholipids at Cell Adhesion Sites

Abstract

The cytoskeletal protein vinculin is a major regulator of cell adhesion and attaches to the cell surface by binding to specific phospholipids. Structural, biochemical, and biological studies provided much insight into how vinculin binds to membranes, what components it recognizes, and how lipid binding is regulated. Here we discuss the roles and mechanisms of phospholipids in regulating the structure and function of vinculin and of its muscle-specific metavinculin splice variant. A full appreciation of these processes is necessary for understanding how vinculin regulates cell motility, migration, and wound healing, and for understanding of its role in cancer and cardiovascular diseases.Inositol phospholipids are crucial regulators of cell physiology, and their head group interactions play fundamental roles in controlling membrane/cytosol interfaces. In addition to signal transduction at the cell surface, these lipids regulate a range of cellular processes including membrane trafficking, polarity, nuclear events, the permeability and transport functions of membranes, and cytoskeletal organization. Phosphoinositides are spatially and temporally regulated at sites of actin assembly andcytoskeletonremodeling.Phosphatidylinositol4,5-bisphosphate (PIP 2 ) 2 is a precursor of the second messengers diacylglycerol, inositol 3,4,5-trisphosphate, and phosphatidyl 3,4,5-trisphosphate and is crucial in the organization of the actin cytoskeleton at the plasma membrane (1). PIP 2 participates in the recruitment and activation of a wide variety of adaptor proteins and actin regulatory proteins. During the assembly of focal adhesions (FAs), the cytoskeletal protein talin recruits an isoform of phosphatidylinositol 4-phosphate 5-kinase (PIP 5 K␥90) that catalyzes the phosphorylation of phosphatidyl 4-phosphate to generate a local enrichment of PIP 2 (2-4). This localized pool of PIP 2 is critical for the subsequent recruitment of FA proteins and maturation of the FAs (5, 6). Vinculin is an early and essential component of nascent cell-matrix adhesion and acts as a scaffold by binding to several actin-organizing proteins. In mature FAs, vinculin is a key component of the "molecular clutch" that mediates the transmission of force from cytoplasmic F-actin to membrane-bound integrins (7-9). Cytosolic vinculin mainly adopts a closed conformation that is kept inactive through extensive hydrophobic interactions of its globular 91-kDa head (VH, residues 1-840) that harbors binding sites for talin, ␣-actinin, or ␣-catenin to VH (10 -13) and its 21-kDa tail (Vt, residues 879 -1066) domains (14, 15), which are connected via a proline-rich linker (Fig. 1, A and B). The intramolecular VH-Vt interaction masks the binding sites of F-actin (16, 17), PIP 2 (18), and raver1 (19,20) to Vt. Cytoplasmic vinculin must be recruited to FAs and activated to expose ligandbinding sites through a complex process that is not completely understood (21).Vinculin is essential during development due to its role in regulating adhesion and motility, as well as cel...

An East Asian Common Variant Vinculin P.Asp841His Was Associated With Sudden Unexplained Nocturnal Death Syndrome in the Chinese Han Population

“…No significant difference of expression and distribution of both SCN5A and VCL were observed between the controls and SUNDS cases. As previously reported, 25 we identified that VCL directly interacts with SCN5A in vivo and in vitro using coimmunoprecipitations ( Figure 3A and 3B). Furthermore, VCL-D841H does not affect this physical association between VCL and SCN5A ( Figure 3C and 3D).…”

“…However, using the strict ACMG guideline‐based definition for pathogenicity, D841H was considered as a variant of uncertain significance. D841H localized to the proline‐rich zone (amino acids 837–878), which links the head domain (residues 1–836, harbors binding sites of talin, α‐actin, or α‐catenin) to tail domain (residues 879–1066, harbors paxillin‐binding site) …”

“…D841H localized to the proline-rich zone (amino acids 837-878), which links the head domain (residues 1-836, harbors binding sites of talin, a-actin, or a-catenin) to tail domain (residues 879-1066, harbors paxillin-binding site). [23][24][25]…”

Differential lipid binding of vinculin isoforms promotes quasi-equivalent dimerization

“…This domain-swapped intermolecular interaction is strengthened by a tryptophan from one meta/vinculin molecule stacking onto a histidine from another meta/vinculin subunit. Significantly, R975 residing on α-helix H1′ in MV that binds to PIP 2 is replaced by an aspartate in vinculin that is not involved in PIP 2 binding to Vt and is the only amino acid that is not conserved in all combined, MVt or Vt, lipid binding residues in the crystal structures (46). Importantly, the DCM/HCM-associated mutant R975W binds PIP 2 but does not dimerize.…”

“…Several mechanisms, binding partners, and modifications have been reported to sever the vinculin head-tail interaction and activate vinculin (46,51). Lipids were originally thought to be involved in activating vinculin (34,36) but inactive vinculin does not bind to PIP 2 (38).…”