Recombinant Rat CAAX prenyl protease 2 (Rce1)

Molecular Definition and Biological Role

Recombinant Rat Rce1 is a 329-amino-acid integral membrane protease expressed in heterologous systems (e.g., E. coli or mammalian cells) with a polyhistidine (His) tag for purification . Its primary function involves endoproteolytic processing of farnesylated or geranylgeranylated CAAX proteins, a step essential for the membrane association of signaling molecules like Ras and Rho GTPases . Unlike geranylgeranylated proteins, farnesylated substrates such as Ras require Rce1-mediated cleavage for correct plasma membrane targeting .

Expression Systems

• Bacterial (E. coli): Yields full-length protein (1–329 aa) with >90% purity, lyophilized in Tris/PBS buffer .

• Mammalian cells: Produces soluble protein with higher post-translational fidelity, provided in liquid or lyophilized form .

Substrate Specificity

• Farnesylated substrates: Human RhoA, Ras isoforms (H-, K-, N-Ras) .

• Geranylgeranylated substrates: Not processed by Methanococcus maripaludis Rce1 homologs but cleaved by eukaryotic variants .

Key Findings

• Localization defects: Rce1 knockout in mouse embryonic fibroblasts (MEFs) mislocalizes farnesylated Ras to cytosol, impairing oncogenic signaling .

• Photoreceptor survival: Retinal Rce1 deficiency disrupts trafficking of phosphodiesterase 6 (PDE6), leading to photoreceptor degeneration .

• Actin remodeling: Geranylgeranylated Rho GTPases (Rac1, Cdc42) remain functional in Rce1⁻/⁻ cells, highlighting lipid-specific processing requirements .

Applications in Disease Research

• Cancer therapeutics: Rce1 inhibition disrupts Ras membrane localization, reducing tumor growth in preclinical models .

• Neurodegeneration: Impaired PDE6 trafficking in Rce1-deficient retinas models retinal dystrophy mechanisms .

• Plant biology: Arabidopsis Rce1 homologs restore plasma membrane localization of ROP GTPases in yeast, confirming evolutionary conservation .

Mechanistic and Inhibitor Studies

Rce1 employs a glutamate-activated water molecule for proteolysis, distinct from aspartyl or metalloprotease mechanisms . Inhibitors like N-acetyl-S-farnesyl-L-cysteine (AFC) block activity by competing with prenylated substrates . Structural data reveal a potential drug-binding site at the TM2–TM4 interface, critical for lipid anchoring .

Challenges and Future Directions

• Isoform complexity: Mammals express two Rce1 splice variants (Iso1/Iso2) with differential regulation by deubiquitinases like USP17 .

• Therapeutic targeting: Developing isoform-specific inhibitors remains challenging due to Rce1’s membrane-embedded architecture .