Absence of integrin α3 modulates the integrin landscape of human keratinocytes

Integrins are among the most abundant cell surface receptors constituting the principal adhesion receptors for the extracellular matrix (ECM), providing a physical anchor for the cell and triggering multiple intracellular signalling events. Loss-of function mutations of the integrin α3 gene (ITGA3) have been recently disclosed in patients with interstitial lung disease, congenital nephrotic syndrome and junctional epidermolysis bullosa, a multiorgan disorder with fatal outcome. In these patients, the respiratory function is strongly impaired and the kidneys are variably affected, whereas skin fragility is rather mild, has a delayed onset after birth or remains unrecognized, suggesting that integrin α3 differently influences the development and homeostasis of these organs. Here we employed authentic human keratinocytes bearing a naturally occurring integrin α3 loss-of-function mutation as a prototype to characterize the molecular mechanisms launched by the constitutional absence of this integrin subunit. To validate our findings, we generated new cellular models, including an additional ILNEB patient cell line, ITGA3 rescued and knockdown cells. We show that keratinocytes lacking a functional α3 subunit have an activated cellular phenotype with a switch in the pattern of integrin α subunits on the cell surface. These assure spreading and adhesion of epidermal keratinocytes but also drive the migratory phenotype of these cells. Cell lines were derived in triplicate from primary keratinocytes of a patient with an ITGA3 loss-of-function homozygous mutation and an age and sex matched healthy donor (designated as control, A3- and Co, respectively) by immortalization with the E6E7 genes of the HPV. Normal human keratinocytes (NHK) were obtained from a healthy donor.