PTAR1 (protein prenyltransferase alpha subunit repeat containing 1) serves as the substrate-recognition α-subunit of geranylgeranyl transferase type 3 (GGTase-3), a newly identified prenyltransferase complex 12. GGTase-3 catalyzes geranylgeranylation of two major substrates: FBXL2, an E3 ubiquitin ligase that requires membrane localization for degrading membrane-anchored proteins 1, and Ykt6, a Golgi SNARE protein that undergoes double prenylation (first farnesylation, then geranylgeranylation) essential for Golgi complex organization and intra-Golgi trafficking 23. PTAR1-dependent Ykt6 double prenylation is critical for lysosomal hydrolase trafficking and autophagy 3, and for glucose- and KCl-stimulated insulin secretion from pancreatic β-cells 4. PTAR1 dysfunction impairs glycosaminoglycan biosynthesis, affecting Golgi morphology and potentially influencing viral attachment and disease pathogenesis 5. Recent evidence identifies PTAR1 as a biomarker associated with diabetic retinopathy pathogenesis through its role in mitochondrial-related inflammatory signaling 6. PTAR1 expression is dynamically regulated during inflammatory responses in periodontal disease 7, suggesting broader roles in innate immunity beyond canonical prenylation functions.