IQGAP3 is an important mediator of the psoriatic phenotype of keratinocytes

Keratinocytes are immunocompetent cells important for the structural and barrier function of skin. Psoriatic keratinocytes are characterized by the enhanced proliferation and reduced differentiation rates as well as by the elevated production of proinflammatory cytokines and chemoattractants. In this research we have knocked-down a scaffold protein IQGAP3 using shRNA in HaCaT keratinocytes (HaCaT_shIQ3) in order to test the hypothesis if IQGAP3 mediates the psoriatic phenotype of keratinocytes. IQGAP interacts with cell adhesion molecules, with the cytoskeleton, with signaling molecules to regulate cell morphology, motility and kinase pathways. Earlier we have identified IQGAP3 to be overexpressed in skin of psoriatic patients and to be stimulated by the proinflammatory cytokines IL17, TNFa and IFNg. RNA-seq of the HaCaT_shIQ3 cells has shown that among the GO enriched by the downregulated genes were: positive regulation of MAPK cascade, negative regulation of inflammatory response, epidermis development, negative chemotaxis, cell adhesion, keratinization, keratinocyte differentiation, intracellular signal transduction. Among the GO enriched by the upregulated genes were positive regulation of macrophage cytokine production, extracellular matrix organization, positive regulation of I-kB/NF-kB signaling, calcium transport, cell adhesion, positive regulation of inflammatory response, lipid metabolic process, positive regulation of IL6 production, NO biosynthetic process. Almost all the onthologies mentioned above are involved in psoriatic process, highlighting the importance of the IQGAP3 for this disease. Using xCELLigence real time cell analysis system we have evaluated the growth rates of HaCaT_shIQ3. Compared to the control cells, HaCaT_shIQ3 demonstrated slower growing rates, delayed wound healing and were in a lesser degree growth-stimulated by psoriatic proinflammatory cytokines. Thus we concluded IQGAP3 to be an important mediator of the psoriatic phenotype of keratinocytes.