Association of the PLIN1 Amphipathic Helix with Membrane Mimetics Shows a Threshold-like Dependence on Phosphatidylglycerol Content

The central amphipathic region of perilipin 1 (PLIN1) contributes to lipid-droplet targeting, but the interfacial properties that govern its association with lipid assemblies remain incompletely defined. Here, we examined human PLIN1 residues 94-193 (PLIN1-AH) by solution nuclear magnetic resonance spectroscopy in dodecylphosphocholine (DPC) micelles and dimyristoyl phosphatidylcholine/dihexanoylphosphatidylcholine (DMPC/DHPC) bicelle-forming assemblies, complemented by biolayer interferometry (BLI) measurements of DMPC/dimyristoyl phosphatidylglycerol (DMPG) large unilamellar vesicle recruitment to immobilized PLIN1-AH. DPC micelles produced extensive spectral reorganization, whereas neutral DMPC/DHPC bicelles caused comparatively modest perturbations. At q = 0.8, increasing DMPG from 25 to 50 mol% shifted the NMR response from a low- to a high-response regime, with no further increase at 75-100 mol%. At 50 mol% DMPG, increasing q to 1.6 further enhanced the spectroscopic response. Vesicle recruitment showed a corresponding nonlinear composition dependence, reaching its maximum at 50 mol% DMPG among the compositions tested. These results indicate that PLIN1-AH association is sensitive to both membrane mimetic organization and anionic-phospholipid content and support a threshold-like transition around 50 mol% DMPG under the conditions tested.