PDCL3

PDCL3 is a phosducin-like chaperone protein that operates in two distinct cellular contexts: cytoskeletal protein folding and receptor tyrosine kinase stabilization (PMID:23792958, PMID:19501098). As the human ortholog of yeast PLP2, PDCL3 engages the CCT (chaperonin-containing TCP-1) chaperonin to regulate beta-actin folding, but unlike its stimulatory yeast counterpart it acts as an inhibitor of CCT-mediated actin folding, an activity conferred by its acidic C-terminal extension (PMID:19501098). In endothelial cells, PDCL3 binds the juxtamembrane domain of VEGFR-2, blocks its ubiquitination and proteasomal degradation, protects the receptor from misfolding and aggregation, and thereby raises VEGFR-2 surface abundance and VEGF-induced tyrosine phosphorylation to drive endothelial proliferation, capillary tube formation, and angiogenesis in zebrafish and mouse models (PMID:23792958, PMID:26059764). This VEGFR-2-stabilizing function is gated by N-terminal methionine acetylation of PDCL3, a modification required for its hypoxia-induced upregulation and its interaction with VEGFR-2 (PMID:26059764). The same VEGFR-2 axis is co-opted in glioma-associated mesenchymal stem cells, where PDCL3 upregulation promotes their conversion to pericytes and enhances vasculogenic mimicry (PMID:40469100). Compound heterozygous loss-of-function variants in PDCL3 cause megacystis-microcolon-intestinal-hypoperistalsis syndrome (MMIHS), linking its actin-folding chaperone role to smooth muscle contractility (PMID:32621347).

1. 2009 High

   Established whether human PDCL3 modulates CCT-dependent cytoskeletal protein folding, and whether it shares the function of its yeast ortholog, defining its core chaperone identity.

   Evidence In vitro CCT-actin folding assay in reticulocyte lysate with C-terminal domain-swap mutagenesis and reconstitution using purified yeast components

   PMID:19501098

   Open questions at the time

   • Mechanism by which the acidic C-terminal extension inhibits CCT not structurally resolved
   • Cellular consequences of actin-folding inhibition in specific tissues not defined
   • Does not address PDCL3's role outside the cytoskeleton
2. 2013 High

   Identified PDCL3 as a direct binding partner and stabilizer of VEGFR-2, answering how the receptor's surface abundance is controlled and extending PDCL3's chaperone role to receptor tyrosine kinase signaling.

   Evidence Yeast two-hybrid screen, co-immunoprecipitation, siRNA knockdown, VEGFR-2 ubiquitination assay, and endothelial tube formation/proliferation assays

   PMID:23792958

   Open questions at the time

   • Structural basis of juxtamembrane-domain binding not resolved
   • Whether VEGFR-2 stabilization requires the CCT machinery not addressed
   • Identity of the ubiquitin ligase blocked by PDCL3 not defined
3. 2015 High

   Defined the upstream regulatory input controlling PDCL3's VEGFR-2 function, showing that N-terminal methionine acetylation couples hypoxia to receptor stabilization and angiogenesis in vivo.

   Evidence Mass spectrometry PTM identification, acetylation-site mutagenesis, protein aggregation assay, and zebrafish and mouse angiogenesis models

   PMID:26059764

   Open questions at the time

   • Enzyme(s) responsible for hypoxia-regulated N-terminal acetylation not identified
   • How acetylation mechanistically promotes VEGFR-2 binding unclear
   • Relationship between the actin-folding and VEGFR-2 functions not integrated
4. 2020 Medium

   Linked PDCL3 to human disease, showing that biallelic loss-of-function causes MMIHS and implicating its chaperone function in smooth muscle contractility.

   Evidence Exome sequencing and cDNA analysis confirming nonsense-mediated decay in affected individuals

   PMID:32621347

   Open questions at the time

   • No direct in vitro functional rescue experiment performed
   • Whether the actin-folding or another function underlies the smooth muscle defect not established
   • Single study without independent patient cohort
5. 2025 Medium

   Extended the PDCL3-VEGFR-2 axis to a tumor microenvironment context, showing PDCL3 drives mesenchymal-to-pericyte transformation and vasculogenic mimicry.

   Evidence siRNA knockdown and overexpression in glioma-associated mesenchymal stem cells with co-culture vasculogenic mimicry assays and Western blot

   PMID:40469100

   Open questions at the time

   • Mechanistic dissection limited to the VEGFR-2 readout
   • Single lab without in vivo tumor confirmation
   • Whether PDCL3 acetylation/hypoxia regulation operates in this context untested

• How PDCL3's two activities — CCT-coupled actin folding and VEGFR-2 stabilization — are mechanistically and structurally related, and which underlies each disease phenotype, remains unresolved.
• No structural model of PDCL3 in either complex
• No unified mechanism connecting actin and VEGFR-2 functions
• Acetyltransferase and deubiquitination/ligase partners unidentified