Inhibition of FAK prevents blister formation in the neonatal mouse model of pemphigus vulgaris

Abstract

Pemphigus vulgaris (PV) is an autoimmune blistering skin disease characterized by suprabasal acantholysis and by autoantibodies against desmoglein 3 localized on desmosomes. In addition, caspases also seem to participate in this blistering disease. Focal adhesion kinase (FAK) is a non-receptor tyrosine kinase involved in cytoskeleton remodelling and formation and disassembly of cell adhesion structures. We have previously demonstrated that HER (human epidermal growth factor receptor related) isoforms, Src (Rous sarcoma) and mammalian target of rapamycin (mTOR), three molecules implicated in signalling processes, take part in suprabasal acantholysis and apoptosis induced by PV-IgG in a mouse model. Our aim was to investigate whether upregulation of FAK is implicated in the development of PV lesions. Herein, using a mouse model, PV-IgG administration showed an increased level of FAK phosphorylated on 397 and 925 tyrosine residues in the basal layer of epidermis.When mice were pretreated with a FAK inhibitor (FI), the acantholysis of the basal layer of epidermis was absent. More interestingly, we observed that phosphorylated FAK (Y397⁄925) decreased when HER isoforms, Src, mTOR and pan-caspases inhibitors were employed before PV-IgG administration. In addition, pretreatment with the FI before PV-IgG injection prevented the changes in both Bax and Bcl-2 expression and caspase-9 and caspase-3 activities induced by PV-IgG. Finally, FI reduced the expression of phosphorylated Src and mTOR in the basal cells of epidermis. In conclusion, our data reveal a novel role of phosphorylated FAK (Y397⁄925) in PV development involving HER isoforms, Src and mTOR kinases.

Mechanisms of Mitochondrial Damage in Keratinocytes by Pemphigus Vulgaris Antibodies

“…In this study, we demonstrated for the fist time dramatic changes in the mitochondria O 2 respiration, dissipation of ⌬⌿ m , and drastic increases in the intracellular levels of ROS. These changes can induce intrinsic apoptosis, which is consistent with observations that PVIgG binding to KCs is associated with mitochondrial damage manifested by cytochrome c release and activation of caspase 9 (17)(18)(19)(20). Because the mode of mitochondrial damage by MtAbs depends on the biological function of targeted protein, the exact primary mechanisms of mitochondrial damage apparently differ from patient to patient, in keeping with striking variations in the disease severity and response to treatment among different PV patients (26).…”

“…We became interested in MtAbs because we sought to elucidate the mechanism of intrinsic apoptosis of KCs in PV originally demonstrated by us (17) and confirmed by others (18,19). The direct evidence that MtAbs are critical to disease pathology, rather than a bystander phenomena in PV, was provided by the studies demonstrating that PV IgGs enter KCs and specifically bind to a number of mitochondrial proteins, which is associated with the mitochondrial damage manifested by cytochrome c release (20).…”

Pemphigus vulgaris antibodies target the mitochondrial nicotinic acetylcholine receptors that protect keratinocytes from apoptolysis

“…PVIgGs bind to a number of mitochondrial self-antigens causing alterations of mitochondrial respiration, dramatic changes in the mitochondrial membrane potential, proton leakage, and increasing the intracellular production of reactive oxygen species and CytC release [23,24]. We have demonstrated that PVIgGs activate the mitochondrial apoptotic pathway in KCs, manifested by elevation of CytC and activation of caspase 9 [24,25], which can trigger the intrinsic apoptotic pathways observed in KCs treated with PVIgGs [26]. Furthermore, adsorption of antimitochondrial antibodies (AMAs) abolishes the ability of PVIgGs to cause acantholysis both in vitro and in vivo [24].…”

Desmosomal Cadherins and Signaling: Lessons from Autoimmune Disease

“…The involvement of p38MAPK is well established, which may require its downstream kinase MAPKAP kinase 2 (MK2) (Berkowitz et al, 2005(Berkowitz et al, , 2006Mao et al, 2013) and epidermal growth factor receptor (EGF-R) and/or Src signaling (Bektas et al, 2013;Chernyavsky et al, 2007;Frusic-Zlotkin et al, 2006;Tsang et al, 2012b). Other molecules implicated in pemphigus are Akt/mTOR and FAK (Gil et al, 2012;Pretel et al, 2009) as well as JNK (Marchenko et al, 2010), CDK-2 (Lanza et al, 2008), PERP (Nguyen et al, 2009) and factors associated with apoptotic signaling such as caspases 3, 6, 8, and 9 as well as Bcl/Bax and others (Li et al, 2009;Marchenko et al, 2010). However, for most signaling pathways the precise mechanisms by which they reduce Dsg-mediated binding and desmosomal integrity are not well understood.…”