DPM1 and SERPINB5 modulate phosphorylation of DSP at S176, which is essential for cell–cell adhesion (a) Graph showing differential phosphorylation sites of DSP in sgDPM1 HaCaT keratinocytes, presented as log₂ fold change (FC) of respective values from sgNT1 control cells. Each dot represents one biological replicate. * indicates P < 0.05, Student’s paired t test. Red bars indicate significantly altered sites. Schematic of the representation of phospho-sites in DSP. (b) Graph showing S176 phosphorylation intensity in sgNT1, sgDPM1, and sgDPM1 SERPINB5-GFP cells. Each dot represents one biological replicate. One-way ANOVA, Dunnett’s multiple comparison test (N = 3). (c) Schematic of the point mutation of S176 to A176 in the head domain of DSP. (d and e) Images and analysis of DSP-GFP and DSP S176A-GFP expression at the cell membrane in sgDPM1 HaCaT keratinocytes. Insets zoomed 2× of original image. Each dot represents individual cells from three biological replicates. Scale bar: 10 µm distance. Unpaired Student’s t test (N = 3). (f and g) Kymographs and mobile fraction analysis derived from FRAP assays were used to measure DSP and DSP-S176A stability at cell–cell contact sites (N = 3). Scale bar on the y-axis = 1 µm. Each dot represents individual cell–cell contact from three biological replicates. Unpaired Student’s t test. (h and i) Dispase-based dissociation assays in sgDPM1 HaCaT keratinocytes upon reconstitution of DSP-GFP and DSP S176A GFP. Unpaired Student’s t test (N = 3). Each dot represents one biological replicate.