Calcium Regulates the Nuclear Localization of Protein Arginine Deiminase 2

Abstract

Protein arginine deiminases (PADs) are calcium-dependent enzymes that mediate the posttranslational conversion of arginine into citrulline. Dysregulated PAD activity is associated with numerous autoimmune disorders and cancers. In breast cancer, PAD2 citrullinates histone H3R26 and activates the transcription of estrogen receptor (ER) target genes. However, PAD2 lacks a canonical Nuclear Localization Sequence (NLS), and it is unclear how this enzyme is transported into the nucleus. Here, we show for the first time that PAD2 translocates into the nucleus in response to calcium signaling. Using BioID2, a proximity-dependent biotinylation method for identifying interacting proteins, we found that PAD2 preferentially associates with ANXA5 in the cytoplasm. Calcium binding to PAD2 weakens this cytoplasmic interaction, which generating a pool of calcium bound PAD2 that can interact with Ran. We hypothesize that this latter interaction promotes the translocation of PAD2 into nucleus. These findings highlight a critical role for ANXA5 in regulating PAD2 and identify an unusual mechanism whereby proteins translocate between the cytosol and nucleus.

Peptidyl Arginine Deiminase 2 (PADI2)-Mediated Arginine Citrullination Modulates Transcription in Cancer

“…Recently, work by the Thompson group had shown that PAD2 translocates into the nucleus in response to calcium signaling. They found that binding of calcium to PADI2 switches its binding from annexin 5 to the RanGTPase in the cytoplasm that promotes translocation of PAD2 into the nucleus [29]. Using a calcium-dependent process, a series of conformational changes eventually produce the correct movement of key active residues, including a free cysteine 645 into positions that are competent for catalysis [30].…”

Deimination Protein Profiles in Alligator mississippiensis Reveal Plasma and Extracellular Vesicle-Specific Signatures Relating to Immunity, Metabolic Function, and Gene Regulation

“…Peptidylarginine deiminases (PADs) are a group of calcium-dependent enzymes that posttranslationally convert arginine into citrulline in target proteins in an irreversible manner (11). Such calcium-mediated deimination/citrullination can lead to structural and sometimes functional changes in target proteins and therefore affect protein function (12,13). A range of proteins known to undergo this posttranslational modification belong to cytoplasmic, nuclear, and mitochondrial targets, and therefore, depending on which target proteins are modified, deimination can for example contribute to the generation of neo-epitopes as well as affecting gene regulation (14)(15)(16)(17)(18)(19)(20)(21)(22).…”

The roles of PAD2‐ and PAD4‐mediated protein citrullination catalysis in cancers

“…10 Without the NLS, part of PAD2 undergoes nuclear translocation to citrullinate arginine residues on histone tails upon calcium regulation. 3,11,12 It has been reported that PAD2 is detectable not only in nuclei in tissue samples from colon cancer patients but also in HCT116 colon cancer cells. 13 PAD4 is normally localized in the nucleus and in cytoplasmic granules of inflammatory cells (macrophages, eosinophils and neutrophils), mammary gland cells, tumor cells and stem cells and is involved in gene transcription and immune system regulation leading to cell inflammation and the immune response.…”

“…Of note, PAD4 is thought to be the only isozyme that can translocate from the cytoplasm to the nucleus with the classic nuclear localization sequence (NLS) 10 . Without the NLS, part of PAD2 undergoes nuclear translocation to citrullinate arginine residues on histone tails upon calcium regulation 3,11,12 . It has been reported that PAD2 is detectable not only in nuclei in tissue samples from colon cancer patients but also in HCT116 colon cancer cells 13 .…”