Proteomic Analysis of Human Angiogenin Interactions Reveals Cytoplasmic PCNA as a Putative Binding Partner

Human Angiogenin (hAng) is a member
of the ribonuclease A superfamily
and a potent inducer of neovascularization. Protein interactions of
hAng in the nucleus and cytoplasm of the human umbilical vein cell
line EA.hy926 have been investigated by mass spectroscopy. Data are
available via ProteomeXchange with identifiers PXD006583 and PXD006584.
The first gel-free analysis of hAng immunoprecipitates revealed many
statistically significant potential hAng-interacting proteins involved
in crucial biological pathways. Surprisingly, proliferating cell nuclear
antigen (PCNA), was found to be immunoprecipitated with hAng only
in the cytoplasm. The hAng–PCNA interaction and colocalization
in the specific cellular compartment was validated with immunoprecipitation,
immunoblotting, and immunocytochemistry. The results revealed that
PCNA is predominantly localized in the cytoplasm, while hAng is distributed
both in the nucleus and in the cytoplasm. hAng and PCNA colocalize
in the cytoplasm, suggesting that they may interact in this compartment.