Comparative interactomics analysis reveals potential regulators of α6β4 distribution in keratinocytes

Abstract

The integrin α6β4 and cytoskeletal adaptor plectin are essential components of type I and type II hemidesmosomes (HDs). We recently identified an alternative type II HD adhesion complex that also contains CD151 and the integrin α3β1. Here, we have taken a BioID proximity labeling approach to define the proximity protein environment for α6β4 in keratinocytes. We identified 37 proteins that interacted with both α6 and β4, while 20 and 78 proteins specifically interacted with the α6 and β4 subunits, respectively. Many of the proximity interactors of α6β4 are components of focal adhesions (FAs) and the cortical microtubule stabilizing complex (CMSC). Though the close association of CMSCs with α6β4 in HDs was confirmed by immunofluorescence analysis, CMSCs have no role in the assembly of HDs. Analysis of the β4 interactome in the presence or absence of CD151 revealed that they are strikingly similar; only 11 different interactors were identified. One of these was the integrin α3β1, which interacted with α6β4 more strongly in the presence of CD151 than in its absence. These findings indicate that CD151 does not significantly contribute to the interactome of α6β4, but suggest a role of CD151 in linking α3β1 and α6β4 together in tetraspanin adhesion structures.

Hemidesmosome-Related Keratin Filament Bundling and Nucleation

“…Basal epidermal cells contain keratins 5 and 14, which have been shown to bind to the hemidesmosomal plakin family cytolinkers plectin 1a [ 15 ] and bullous pemphigoid antigen 1 (BPAG-1; also referred to as BPAG-1e or BP230) [ 16 ]. These linker molecules, in turn, facilitate the attachment to the hemidesmosome-specific α6β4-integrin heterodimers [ 6 , 17 ], which bind to laminin 332 in the basement membrane [ 18 , 19 ]. Type II hemidesmosomes of simple epithelia consist only of α6β4-integrin heterodimers and plectin 1a-attached keratins, whereas type I hemidesmosomes, which occur in basal cells of pseudostratified and stratified epithelia, contain additional proteins, such as BPAG-1, the tetraspanin CD151, and the laminin 332-binding BPAG-2 (also referred to as BP180 or collagen type XVII) [ 6 , 20 ].…”

Junctional epithelium and hemidesmosomes: Tape and rivets for solving the “percutaneous device dilemma” in dental and other permanent implants

“…Indeed, integrin α6β4 involvement in the Rho-ROCK (Rho-associated protein kinase)-MLC and FAK (focal adhesion kinase)-PI3K signaling pathways has been well demonstrated [ 81 ]. Generation of such signaling hubs at integrins likely drives the 135 integrin α6β4 interactors [ 132 ].…”

Regulation of hemidesmosome dynamics and cell signaling by integrin α6β4

“…Microtubules are targeted and captured at the plasma membrane by the cortical microtubule stabilizing complex (CMSC), which is localized in close proximity to FAs and plays a role in their dynamics (Chen et al, 2018). Although CMSCs are also found in the vicinity of HDs, these complexes do not appear to contribute to the formation and/or disassembly of HDs (Hotta et al, 2010;te Molder et al, 2020).…”

“…Zinc finger DHHC-type palmitoyltransferase 3 (ZDHHC3) is responsible for β4 palmitoylation in breast and prostate carcinoma cells (Sharma et al, 2008). In contrast, ZDHHC5, but not ZDHHC3, might contribute to α6β4 palmitoylation in keratinocytes, as this acyltransferase has been identified as a potential interactor of both the α6 and β4 subunits by proximity labeling in these cells (te Molder et al, 2020). The function of β4 palmitoylation still has to be defined.…”