Self-regulated Cleavage of the Mitochondrial Intramembrane-cleaving Protease PARL Yields Pβ, a Nuclear-targeted Peptide

Abstract

Regulated intramembrane proteolysis (RIP) is an emerging paradigm in signal transduction. RIP is mediated by intramembrane-cleaving proteases (I-CliPs), which liberate biologically active nuclear or secreted domains from their membrane-tethered precursor proteins. The yeast Pcp1p/Rbd1p protein is a Rhomboid-like I-CliP that regulates mitochondrial membrane remodeling and fusion through cleavage of Mgm1p, a regulator of these essential activities. Although this ancient function is conserved in PARL (Presenilins-associated Rhomboid-like protein), the mammalian ortholog of Pcp1p/Rbd1p, the two proteins show a strong divergence at their N termini. However, the N terminus of PARL is significantly conserved among vertebrates, particularly among mammals, suggesting that this domain evolved a distinct but still unknown function. Here, we show that the cytosolic N-terminal domain of PARL is cleaved at positions 52-53 (␣-site) and 77-78 (␤-site). Whereas ␣-cleavage is constitutive and removes the mitochondrial targeting sequence, ␤-cleavage appears to be developmentally controlled and dependent on PARL I-CliP activity supplied in trans. The ␤-cleavage of PARL liberates P␤, a nuclear targeted peptide whose sequence is conserved only in mammals. Thus, in addition to its evolutionarily conserved function in regulating mitochondrial dynamics, PARL might mediate a mammalian-specific, developmentally regulated mitochondriato-nuclei signaling through regulated proteolysis of its N terminus and release of the P␤ peptide.

Hax1 lacks BH modules and is peripherally associated to heavy membranes: implications for Omi/HtrA2 and PARL activity in the regulation of mitochondrial stress and apoptosis

“…However, this appears to be an unlikely possibility because loss of Hax1 function only partially reduces the expression of a cleaved form of Omi/HtrA2. Further, genetic ablation of Hax1 compromises neither Opa1 cleavage (10) nor PARL (β-cleavage (Figure 6), an N-terminal processing that requires PARL activity supplied in trans (33). Together, these results indicate that Hax1 is not a PARL substrate-presenting protein, as it has been recently discussed (34), and that PARL rhomboid activity does not require Hax1.…”

CHMP5 is essential for late endosome function and down-regulation of receptor signaling during mouse embryogenesis

“…These experiments typically involve the complete digestion of exposed domains of proteins on the outside of a sealed compartment and the protection of those domains or proteins that reside on the inside of the compartment (Wu et al, 2003; Sik et al, 2004). To apply the protease protection assay to our system, we modified the original protocol of the protease protection assay.…”

Association of PARL Gene Rs3732581, Rs73887537 Polymorphisms with Type 2 Diabetes Mellitus, Insulin Resistance and Blood Lipid Levels in Chinese Population

“…Indeed, the release of the Pβ-peptide, the putative effectors molecule of the PARL signaling, is self-regulated. The β-cleavage is either executed by an unknown protease (PARLase) that is activated via a PARL-catalyzed cleavage or by PARL itself through an intermolecular reaction [46]. The proteolytic activity of PARL required for the β-cleavage of its N terminus could be supplied in trans [46].…”

“…PARL is the only intramembrane-cleaving protease where the putative signaling moiety is also part of the protease itself. The β-cleavage of PARL releases within the mitochondrial matrix a 25 amino acid-long peptide termed Pβ-peptide which appears to execute mitochondrial retrograde signaling (MRS) [46][47][48]. MRS senses mitochondrial activities/dysfunctions and relay this information to the nucleus in order to initiate appropriate physiological readjustments including metabolism [48].…”

“…The β-cleavage is either executed by an unknown protease (PARLase) that is activated via a PARL-catalyzed cleavage or by PARL itself through an intermolecular reaction [46]. The proteolytic activity of PARL required for the β-cleavage of its N terminus could be supplied in trans [46]. So, it is tempting to speculate that the PARL rs3732581 genetic variant could in some way influence the MRS and metabolism of lipid through alter the conformation of the protein and its proteolytic activity.…”