The actin binding protein α-adducin modulates desmosomal turnover and plasticity

Abstract

Short Title: α-adducin modulates desmosomal turnover 2 ABBREVIATIONS: Add1 = α-adducin; AFM = atomic force microscope; BSA = bovine serum albumin; ctrl = control; Dsg = desmoglein; E-Cad = cadherin; FDC = force-distance curve; FRAP = fluorescent recovery after photobleaching; ko = knockout; MEK = murine keratinocyte; scFv = single chain variable fragment; wt = wildtype; ORCIDs:ABSTRACT Intercellular adhesion is essential for tissue integrity and homeostasis. Desmosomes are especially abundant in the epidermis and the myocardium, tissues, which are under constantly changing mechanical stresses. Yet, it is largely unclear whether desmosomal adhesion can be rapidly adapted to changing demands and the mechanisms underlying desmosome turnover are only partially understood. We here show that loss of the actin-binding protein α-adducin prevented the ability of cultured keratinocytes or murine epidermis to withstand mechanical stress paralleled with reduced desmosome number. This effect was not caused by decreased levels or impaired adhesive properties of desmosomal molecules but rather by altered desmosome turnover. Mechanistically, reduced cortical actin density in α-adducin knockout keratinocytes resulted in increased mobility of the desmosomal adhesion molecule desmoglein 3 (Dsg3) and impaired interactions with Ecadherin, a crucial step in desmosome formation. Accordingly, loss of α-adducin prevented increased membrane localization of Dsg3 in response to cyclic stretch or shear stress. Our data demonstrate plasticity of desmosomal molecules in response to mechanical stimuli and unravel a mechanism how the actin cytoskeleton indirectly shapes intercellular adhesion by restricting the mobility of desmosomal molecules.

The inotropic agent digitoxin strengthens desmosomal adhesion in cardiac myocytes in an ERK1/2-dependent manner

“…Previous studies identified these surface molecules at least in part to be DSG2 molecules providing homophilic interactions [33,35]. As shown for different cell types, desmosomal cadherins present on the cell surface can co-localize to desmosomal plaque proteins and intermediate filaments [43,46,47], which might function as a reserve pool for desmosome assembly [16,35]). For AFM studies, these desmosomal precursors can serve as surrogates to study desmosomal adhesion.…”

Autoantibody-Specific Signalling in Pemphigus

“…All these effects can be explained by the fact that RhoA via Rho kinase regulates the actin binding protein adducin ( 192 ). Adducin is essential for cell adhesion in keratinocytes by controlling the incorporation of Dsg3 into desmosomes ( 193 ). Other actin binding proteins such as cortactin, which have been shown to be involved in pemphigus pathogenesis, also bind to extra-desmosomal Dsg3 and thus may participate in desmosome assembly ( 191 ).…”

“…Because PKC downstream of PLC/Ca 2+ has been shown to regulate desmosome stability via phosphorylation of DP, the modulation of DP cytoskeletal anchorage may be a promising target for therapy. Similarly, given that p38MAPK induces pathogenic effects via inhibition of RhoA, which via Rho kinase and adducin phosphorylation is important for desmosome assembly ( 190 , 192 , 193 , 227 ), therapeutic approaches to stimulate desmosome assembly should be characterised in more detail. Finally, since the small inhibitor library helped to identify a role in keratinocyte adhesion regulation for VEGFR2, TrkA, PI3K, and PDK1 ( Table 2 ), new candidates for treatment options have been elucidated as well ( 229 ).…”

“…In a next step, Dsg molecules are transferred to DP coupled to keratin filaments (9,189). Actin binding proteins such as adducing, which is regulated via RhoA/Rho kinase, and cortactin are important for directed targeting of Dsg molecules during desmosome assembly (190)(191)(192)(193). The assembly of Dsgs with DP is controlled by PKP3 in a Rap1-dependent manner (194), the latter of which is a GTPase activated by cAMP and EPAC1.…”

Defective Desmosomal Adhesion Causes Arrhythmogenic Cardiomyopathy by involving an Integrin-αVβ6/TGF-β Signaling Cascade

“…Murine keratinocytes were isolated from the epidermis of DSG2-W2A mut/mut and wt/wt mice and immortalized as described. 59 In Brief, the epidermis of neonatal mice was separated from the dermis via incubation in dispase II solution (>2. ng/ml murine epidermal GF (Invitrogen, Carlsbad, CA), 1 mmol/l sodium pyruvate, 0.18 mmol/l adenine, 120 pmol/l cholera toxin, 5 µg/ml insulin, and 500 ng/ml hydrocortisone (all Sigma-Aldrich). Cells were kept in an incubator at 35 °C with 5 % CO2 and full humidity, the medium was changed every third day.…”