Nucleoporin 210kDa

Nuclear pore glycoprotein-210 (gp210) is an essential trafficking regulator in the eukaryotic nuclear pore complex. Gp-210 anchors the pore complex to the nuclear membrane.^[1] and protein tagging reveals its primarily located on the luminal side of double layer membrane at the pore. A single polypeptide motif of gp210 is responsible for sorting to nuclear membrane,^[2] and indicate the carboxyl tail of the protein is oriented toward the cytoplasmic side of the membrane.

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Disassembly and Assembly

During eukaryotic mitosis the nuclear envelope disentegrates into vesicles dispersing nuclear lamina proteins and nuclear pore complexes. Nup210 is specifically phosphorylated on the C-terminal (cytoplasmic) domain in mitosis at Ser1880^[3] and is dispersed through out the endoplasmic reticulum during mitosis as homodimers.^[4] Nuclear lamins begin to reassemble around chromosomes at the end of mitosis.^[5] Nup210 lags the reassembly process relative to other Nups.^[6] and while much of the assembly process can occur without it, the final assembly and dilation of the complexes require nup210.^[7] The replacement of serine at position 1880 with a phosphorylated 'looking' glutamate results in Nup120 complexes that fail to reassemble indicating that dephosphorylation of Nup120 within the final phases of proper assembly is required.^[8]

Pathology

Recognized by anti-nuclear antibodies found in primary biliary cirrhosis (PBC) anti-Nup210 antibodies correlate with progression toward end stage liver disease. Nup210 is possibly a destructive autoimmune target of the disease. One idea for the loss of tolerance is the increased or abnormal expression of Nup120 in patients with PBC.^[9]

anti-mitochondral, anti-centromere and anti-nup62 are also found in PBC.

References