The Nuclear Envelope Protein, LAP1B, Is a Novel Protein Phosphatase 1 Substrate

Abstract

Protein phosphatase 1 (PP1) binding proteins are quintessential regulators, determining substrate specificity and defining subcellular localization and activity of the latter. Here, we describe a novel PP1 binding protein, the nuclear membrane protein lamina associated polypeptide 1B (LAP1B), which interacts with the DYT1 dystonia protein torsinA. The PP1 binding domain in LAP1B was here identified as the REVRF motif at amino acids 55-59. The LAP1B:PP1 complex can be immunoprecipitated from cells in culture and rat cortex and the complex was further validated by yeast co-transformations and blot overlay assays. PP1, which is enriched in the nucleus, binds to the N-terminal nuclear domain of LAP1B, as shown by immunocolocalization and domain specific binding studies. PP1 dephosphorylates LAP1B, confirming the physiological relevance of this interaction. These findings place PP1 at a key position to participate in the pathogenesis of DYT1 dystonia and related nuclear envelope-based diseases.

Lamina-associated polypeptide 1: Protein interactions and tissue-selective functions

“…This topology predicts that the amino-terminal domain binds lamins within the nucleus, an interaction likely responsible for LAP1 concentration in the inner nuclear membrane. The amino-terminal domain of LAP1 is also in a position to bind nucleoplasmic proteins such as PP1 [22], as well as the nucleoplasmic domains of other integral inner nuclear membrane proteins. The carboxyl-terminal domain within the perinuclear space has the potential to bind to proteins translocated into the endoplasmic reticulum and the luminal domains of other integral proteins of the inner nuclear membrane.…”

BRI2 Processing and Its Neuritogenic Role Are Modulated by Protein Phosphatase 1 Complexing

“…The SH‐SY5Y human neuroblastoma cell line was maintained in Minimal Essential Medium/F‐12 Nutrient Mixture (Gibco) using procedures previously described [Santos et al, ]. Transient transfections of SH‐SY5Y cells with the following constructs: Myc‐BRI2; Myc‐BRI2 3 KVTA 6 ; and Myc‐BRI2 3 KATA 6 (mutated in the consensus PP1 binding motif 3 KVTF 6 ; PP1‐BM mutants) were performed using TurboFect reagent (ThermoFisher Scientific) according to the manufacturer's protocols.…”

Rif1-Dependent Regulation of Genome Replication in Mammals

“…If PP1 is indeed the sole, ultimate effector of Rif1 function, another protein has to be responsible for recruiting PP1 at RADs-LB + in Rif1 null cells. This is in principle possible, as the PP1 phosphatase has been identified as a partner of different proteins associated with the nuclear envelope, such as AKAP149 (Steen et al, 2000) and LAP1β (Santos et al, 2013).…”