Novel Nuclear Nesprin-2 Variants Tether Active Extracellular Signal-regulated MAPK1 and MAPK2 at Promyelocytic Leukemia Protein Nuclear Bodies and Act to Regulate Smooth Muscle Cell Proliferation

Abstract

Nuclear and cytoplasmic scaffold proteins have been shown to be essential for temporal and spatial organization, as well as the fidelity, of MAPK signaling pathways. In this study we show that nesprin-2 is a novel extracellular signal-regulated MAPK1 and 2 (ERK1/2) scaffold protein that serves to regulate nuclear signaling by tethering these kinases at promyelocytic leukemia protein nuclear bodies (PML NBs). Using immunofluorescence microscopy, GST pull-down and immunoprecipitation, we show that nesprin-2, ERK1/2, and PML colocalize and bind to form a nuclear complex. Interference of nesprin-2 function, by either siRNA-mediated knockdown or overexpression of a dominant negative nesprin-2 fragment, augmented ERK1/2 nuclear signaling shown by increased SP1 activity and ELK1 phosphorylation. The functional outcome of nesprin-2 disruption and the resultant sustained ERK1/2 signal was increased proliferation. Importantly, these activities were not induced by previously identified nuclear envelope (NE)-targeted nesprin-2 isoforms but rather were mediated by novel nuclear isoforms that lacked the KASH domain. Taken together, this study suggests that nesprin-2 is a novel intranuclear scaffold, essential for nuclear ERK1/2 signaling fidelity and cell cycle progression.

Novel Clinically Relevant Genes in Gastrointestinal Stromal Tumors Identified by Exome Sequencing

“…Interestingly, SYNE2 encodes for a nuclear outer membrane protein and has been shown to play a role in MAP kinase signaling pathways (MAPK1 and MAPK2) in promyelocytic leukemia protein (41). SYNE2 also interacts with MAPK8IP2, which is one of our candidate genes on chromosomes 22 (42), and a correlation of expression of these 2 proteins was also seen in our study.…”

Defective DNA-damage repair induced by nuclear lamina dysfunction is a key mediator of smooth muscle cell aging

“…Although the importance of the nuclear lamina in the organization of this complex remains to be confirmed, nesprin-2, PML and ERK1/2 have all been described to associate with the nuclear lamina [36][37][38]. Importantly, disruption of this complex deregulates nuclear ERK1/2 activity and increases VMSC proliferation, confirming the importance of correct spatial regulation of nuclear ERK1/2 signalling [35]. Intriguingly, PML NBs and Table 1 Summary of known lamin A-, prelamin A-and progerin-binding partners involved in NE and chromatin organization, DNA repair and nuclear signalling + + , Confirmed interaction; + , low-affinity interaction; + + + , high-affinity interaction; − , no interaction detected.…”

“…In addition, the nuclear lamina can associate indirectly, via lamin-binding proteins, with signalling molecules to spatially and temporally regulate their activity. For example, we have recently described the lamin A-binding protein nesprin-2 as a nuclear ERK (extracellular-signal-regulated kinase) 1/2 scaffold protein that tethers these kinases at PML NBs in VSMCs [35]. Although the importance of the nuclear lamina in the organization of this complex remains to be confirmed, nesprin-2, PML and ERK1/2 have all been described to associate with the nuclear lamina [36][37][38].…”

Nesprins in Cell Stability and Migration

“…Likewise KASH-less Nesprins affect signal transduction by acting as a scaffold for ERK1/2 to tether these kinases to promyelocytic leukemia protein (PML) nuclear bodies. Loss of Nesprin-2 leads to a sustained ERK1/2 activation and increased cell proliferation [ 49 ]. Finally Nesprins might affect the gene expression profi le of a cell by associating with heterochromatic DNA as demonstrated by chromatin immunoprecipitation (ChIP) experiments.…”