The nucleoporin-like protein NLP1 (hCG1) promotes CRM1-dependent nuclear protein export

Abstract

SummaryTranslocation of transport complexes across the nuclear envelope is mediated by nucleoporins, proteins of the nuclear pore complex that contain phenylalanine-glycine (FG) repeats as a characteristic binding motif for transport receptors. CRM1 (exportin 1), the major export receptor, forms trimeric complexes with RanGTP and proteins containing nuclear export sequences (NESs). We analyzed the role of the nucleoporin-like protein 1, NLP1 (also known as hCG1 and NUPL2) in CRM1-dependent nuclear transport. NLP1, which contains many FG repeats, localizes to the nuclear envelope and could also be mobile within the nucleus. It promotes the formation of complexes containing CRM1 and RanGTP, with or without NES-containing cargo proteins, that can be dissociated by RanBP1 and/or the cytoplasmic nucleoporin Nup214. The FG repeats of NLP1 do not play a major role in CRM1 binding. Overexpression of NLP1 promotes CRM1-dependent export of certain cargos, whereas its depletion by small interfering RNAs leads to reduced export rates. Thus, NLP1 functions as an accessory factor in CRM1-dependent nuclear protein export.

Several Phenylalanine-Glycine Motives in the Nucleoporin Nup214 Are Essential for Binding of the Nuclear Export Receptor CRM1

“…RanGAP (40), CRM1-His (41), Ran (42), His-SPN1 (43), and MPB-Nup214 aa 1859 -2090 (20) were purified as described before. Ran was loaded with GDP or GTP as described previously (39).…”

The amino terminus extension in the long dipeptidyl peptidase 9 isoform contains a nuclear localization signal targeting the active peptidase to the nucleus

“…Quantification was essentially performed as described in [37]. In short, graphs are a result of at least two independent experiments, each in duplicates, and each single experiment contained more than 340 cells.…”

“…So far, no nuclear candidate substrates for these peptidases are known. the only endogenous DPP9 substrate known so far is the RU1 [34][35][36][37][38][39][40][41] antigen, which is stabilized in the cytosol upon DPP9 silencing, linking DPP9 to the MhC class I pathway [28]. Recently, a large degradome screen from cells overexpressing DPP9 or DPP8 was performed, leading to the identification of several cytosolic candidate substrates [27].…”

“…Silencing experiments show that DPP9 and not DPP8 is rate-limiting for the hydrolysis of prolinecontaining peptides in the cytosol suggesting that DPP9 may have a house-keeping role for amino acid homeostasis [28]. the first identified endogenous substrate of DPP9 was the tumor-related epitope RU1 [34][35][36][37][38][39][40][41][42] . Its hydrolysis by DPP9 results in its limited presentation on MhC class I molecules to the immune system linking DPP9 to the MhC class I antigen presentation pathway [28][29][30].…”

Identification of CRM1-dependent Nuclear Export Cargos Using Quantitative Mass Spectrometry

“…As the affinity of many NES substrates for CRM1 is rather low, the formation of this trimeric transport complex seems to be a rate-limiting step in nuclear export (20). On the nuclear side of the NPC, a number of accessory factors such as RanBP3 (21,22), Nup98 (23), and NLP1 (24) can further promote the formation of export complexes. Following export, RanBP1 and RanGAP initiate the disassembly of the export complex (for a review, see Ref.…”