Di-arginine and FFAT-like motifs retain a subpopulation of PRA1 at ER-mitochondria membrane contact sites

Abstract

Prenylated Rab Acceptor 1 (PRA1/Rabac1) is a four-pass transmembrane protein that has been found to localize to the Golgi and promiscuously associate with a diverse array of Rab GTPases. We have previously identified PRA1 to be among the earliest significantly down-regulated genes in the rd1 mouse model of retinitis pigmentosa, a retinal degenerative disease. Here, we show that an endogenous subpopulation of PRA1 resides within the endoplasmic reticulum (ER) at ER-mitochondria membrane contact sites in cultured mammalian cells. We also demonstrate that PRA1 contains two previously unidentified ER retention/retrieval amino acid sequences on its cytosolic N-terminal region: a membrane distal di-arginine motif and a novel membrane proximal FFAT-like motif. Using a truncation construct that lacks complete Golgi targeting information, we show that mutation of either motif leads to an increase in cell surface localization, while mutation of both motifs exhibits an additive effect. We also present evidence that illustrates that N- or C- terminal addition of a tag to full-length PRA1 leads to differential localization to either the Golgi or reticular ER, phenotypes that do not completely mirror endogenous protein localization. The presence of multiple ER retention motifs on the PRA1 N-terminal region further suggests that it has a functional role within the ER.

The Temporal Progression of Retinal Degeneration and Early-Stage Idebenone Treatment in the Pde6b rd1/rd1 Mouse Model of Retinal Dystrophy

“…The Prenylated Rab Acceptor 1 (PRA1/Rabac1) is an essential four-pass transmembrane protein situated in the Golgi apparatus, and plays a crucial role in the process of protein tra cking. It was found to be signi cantly downregulated in the rd1 mouse retina at P2 [20] and was inherently located within the endoplasmic reticulum (ER), speci cally at the membrane contact sites between the ER and mitochondria [21]. We propose that organelles such as the mitochondria, Golgi apparatus, and endoplasmic reticulum may have reciprocal in uences.…”

The temporal progression of retinal degeneration and early-stage idebenone treatment in the Pde6brd1/rd1 mouse model of retinal dystrophy

“…The Prenylated Rab Acceptor 1 (PRA1/Rabac1) is an essential four-pass transmembrane protein situated in the Golgi apparatus and plays a crucial role in the process of protein trafficking. It was found to be significantly downregulated in the rd1 mouse retina at P2 34 and was inherently located within the endoplasmic reticulum (ER), specifically at the membrane contact sites between the ER and mitochondria 35 . We propose that organelles such as the mitochondria, Golgi apparatus, and endoplasmic reticulum may have reciprocal influences.…”