PFN2

PFN2 is an actin-binding protein whose roles extend beyond cytoskeletal regulation to encompass enzymatic cofactor activity, endocytic control of signaling, and post-transcriptional gene regulation. PFN2 forms a ternary complex with NAA80 and actin, binding NAA80 through a proline-rich loop and stimulating its N-terminal acetyltransferase activity toward actin (PMID:32978259). Through its interaction with dynamin, PFN2 modulates endocytosis rates in embryonic stem cells, thereby controlling ERK signaling, cell cycle progression, and differentiation; its levels are post-transcriptionally tuned by miR-290 family microRNAs and an iron response element in its 3′ UTR to coordinate FGF/ERK and Wnt signaling during lineage specification (PMID:32788350). PFN2 is subject to cIAP1-mediated ubiquitin-proteasome degradation influencing cellular ROS levels (PMID:30352681), its mRNA is stabilized by the m6A reader hnRNPA2B1 to promote ferroptosis during ischemia-reperfusion injury (PMID:40010516), and it recruits the RNA-binding protein YBX-1 to stabilize SIX2 mRNA and activate MAPK/JNK signaling in gastric cancer (PMID:39256760).

1. 2018 Medium

   The question of how PFN2 protein levels are controlled was addressed by identifying cIAP1 as an E3 ubiquitin ligase that targets PFN2 for proteasomal degradation, establishing that PFN2 turnover is regulated by the ubiquitin-proteasome system with downstream consequences for intracellular ROS.

   Evidence Ubiquitination assays, proteasome inhibitor experiments, and ROS measurements in cell lines

   PMID:30352681

   Open questions at the time

   • Ubiquitin chain linkage specificity not fully defined
   • Physiological contexts triggering cIAP1-dependent PFN2 degradation not established
   • No independent replication
2. 2020 High

   How PFN2 contributes to enzymatic function beyond its canonical actin-monomer sequestration role was resolved by demonstrating that PFN2 serves as a stable cofactor for the actin N-terminal acetyltransferase NAA80, forming a ternary NAA80–PFN2–actin complex that enhances catalytic activity.

   Evidence Interaction proteomics, analytical ultracentrifugation, in vitro acetyltransferase assays, NAA80 proline-rich loop deletion mutagenesis, and SAXS structural analysis

   PMID:32978259

   Open questions at the time

   • Atomic-resolution structure of the ternary complex not determined
   • In vivo contribution of PFN2-dependent actin acetylation to cellular phenotypes not tested
3. 2020 High

   The mechanism by which miRNAs regulate endocytosis and stemness was clarified by showing that miR-290-mediated suppression of PFN2 controls dynamin-dependent endocytosis, ERK signaling, and cell cycle progression in embryonic stem cells.

   Evidence Pfn2 knockout, PFN2-dynamin interaction domain disruption, 3′ UTR miR-290 binding site mutagenesis, endocytosis and ERK signaling readouts in ESCs

   PMID:32788350

   Open questions at the time

   • Direct structural basis of PFN2–dynamin interaction not resolved
   • Whether PFN2-dynamin regulation extends to somatic cell endocytosis not tested
4. 2021 Medium

   Transcriptional regulation of PFN2 under metabolic stress was established by showing that ets1 and KMT5A co-occupy the PFN2 promoter, with high glucose reducing KMT5A/H4K20me1 to derepress PFN2 and drive endothelial-to-mesenchymal transition in diabetic nephropathy.

   Evidence ChIP, dual luciferase assays, siRNA knockdown, and overexpression in HUVECs

   PMID:34238215

   Open questions at the time

   • Whether ets1-KMT5A regulation of PFN2 operates in non-endothelial cell types not tested
   • Genome-wide specificity of KMT5A repression at the PFN2 locus not assessed
5. 2022 Medium

   OCT1 was identified as a direct transcriptional activator of PFN2 in AR-negative prostate cancer, linking PFN2 to migration and in vivo tumor growth.

   Evidence ChIP-seq in patient-derived cells, siRNA knockdown, migration assays, and xenograft tumor growth

   PMID:35413990

   Open questions at the time

   • Mechanism by which PFN2 promotes migration in this context (actin dynamics vs. signaling) not dissected
   • Single lab, single cancer subtype
6. 2024 Medium

   A positive feedback loop between SIX2 and PFN2 was uncovered in gastric cancer: SIX2 directly activates PFN2 transcription, and PFN2 recruits YBX-1 to stabilize SIX2 mRNA, activating MAPK/JNK signaling and cancer stemness.

   Evidence ChIP, Co-IP and IP-MS for PFN2–YBX1 interaction, RNA stability assays, gain/loss-of-function experiments

   PMID:39256760

   Open questions at the time

   • Whether PFN2–YBX1 interaction is direct or within a larger RNP complex not resolved
   • Generality of SIX2–PFN2 loop beyond gastric cancer not tested
7. 2024 Medium

   Dual post-transcriptional control of PFN2 via a 3′ UTR iron response element and miR-290 site was shown to coordinate two distinct signaling steps—FGF/ERK exit from pluripotency and Wnt-driven mesendoderm specification—during ESC differentiation (preprint).

   Evidence (preprint) 3′ UTR element deletion mutagenesis, ESC differentiation assays, FGF/ERK and Wnt/β-catenin readouts

   PMID:bio_10.1101_2024.10.02.616359

   Open questions at the time

   • Not yet peer-reviewed
   • Iron-responsive trans-factor binding the PFN2 IRE not identified
   • Mechanism linking PFN2 protein levels to Wnt pathway activation unknown
8. 2025 Medium

   The epitranscriptomic regulation of PFN2 was established by showing that the m6A reader hnRNPA2B1 binds an m6A site on PFN2 mRNA to stabilize it, elevating PFN2 and promoting ferroptosis during myocardial ischemia-reperfusion injury.

   Evidence RNA immunoprecipitation, m6A site identification, mRNA stability assays, epistasis experiments (hnRNPA2B1 OE + PFN2 KD), OGD/R in vitro and MIRI in vivo models

   PMID:40010516

   Open questions at the time

   • Direct mechanism by which elevated PFN2 drives ferroptosis (lipid peroxidation, iron handling) not dissected
   • Single lab, no independent replication

• The direct molecular mechanism by which PFN2 protein levels regulate ferroptosis, Wnt signaling, and ROS homeostasis—and whether these reflect a common PFN2 activity or context-dependent functions—remains unresolved.
• No unified mechanistic model linking PFN2's actin/dynamin-binding activities to its roles in ROS/ferroptosis
• Structural basis of PFN2–YBX1 and PFN2–dynamin interactions not determined
• Whether PFN2's cofactor role for NAA80 is relevant to its disease-associated phenotypes not tested