CFAP45

CFAP45 (NESG1/CCDC19) is an axonemal protein that supports motile ciliary and flagellar beating by maintaining adenine nucleotide homeostasis within the axoneme (PMID:33139725). It binds AMP and forms part of a module with dynein ATPases, adenylate kinase AK8, and CFAP52, where the modeled AMP-binding interface couples CFAP45 to AK8; dyskinetic microtubule sliding in Cfap45-deficient sperm is rescued by supplementing AMP or ADP with ATP, establishing that CFAP45 sustains the nucleotide pool that dynein-driven sliding consumes (PMID:33139725). CFAP52 physically interacts with CFAP45 in the sperm flagellum and is required for its stable expression, linking the two as interdependent components of this beating module (PMID:37236356). Within the axoneme CFAP45 occupies a punctate, static position, and its depletion destabilizes cilia and causes their detachment from the apical surface, producing left-right patterning and cardiac looping defects (PMID:37172641). In epithelial cancer cell contexts CFAP45 acts as a growth-suppressive factor: its induced expression in nasopharyngeal carcinoma cells reduces proliferation, G1-S transition, migration, invasion, and xenograft tumorigenesis while regulating the cell cycle regulators CCNA1 and p21 (PMID:20715168), and it suppresses migration and invasion through a miR-1254/HDGF axis that blocks Wnt/β-catenin-driven β-catenin nuclear translocation and EMT (PMID:33718512).

1. 2010 Medium

   Established that CFAP45 (NESG1) can act as a growth- and invasion-suppressive factor, the first functional handle on the protein, framing it as a candidate tumor suppressor in nasopharyngeal carcinoma.

   Evidence Lentiviral overexpression in NPC cells with proliferation, cell cycle, invasion/migration assays and xenograft tumorigenesis, with CCNA1/p21 readouts

   PMID:20715168

   Open questions at the time

   • No direct molecular mechanism linking CFAP45 to CCNA1/p21 regulation
   • Does not address the protein's ciliary/axonemal role
   • Overexpression-based phenotype, no endogenous loss-of-function
2. 2012 Low

   Asked which effectors mediate the growth-suppressive phenotype and implicated ENO1 as a CFAP45-regulated protein opposing its control of cell cycle regulators.

   Evidence 2D gel proteomics of NESG1-overexpressing NPC cells with western blot and ENO1 overexpression rescue

   PMID:22997098

   Open questions at the time

   • Indirect mechanism; no direct CFAP45-ENO1 binding shown
   • Single lab, screen-based with limited validation
   • Causal ordering between CFAP45 and ENO1 not resolved
3. 2014 Low

   Connected CFAP45 (CCDC19) to a miRNA-mediated signaling output, positing that it suppresses growth through miR-184 and the PI3K/AKT/c-Jun axis.

   Evidence Lentiviral overexpression and shRNA knockdown in NSCLC cells with proliferation, cell cycle, and pathway western blots

   PMID:24976536

   Open questions at the time

   • No direct binding assay between CCDC19 and miR-184
   • Pathway inference is indirect via OE/KD
   • Mechanism of miRNA induction unknown
4. 2019 Low

   Probed an interaction partner and proposed CFAP45 (NESG1) cooperates with VPS33B to relieve PI3K/AKT/c-Jun-mediated transcriptional repression in NPC cells.

   Evidence Co-localization microscopy and NESG1 knockdown rescue with PI3K/AKT/c-Jun western blots

   PMID:30944308

   Open questions at the time

   • Interaction rests on co-localization, not direct biochemistry
   • Single lab, single method for the interaction claim
   • Functional link to ciliary biology unaddressed
5. 2021 Medium

   Extended the VPS33B link to a Co-IP-confirmed interaction in ovarian cancer and to a Wnt/β-catenin-suppressive miR-1254/HDGF axis, sharpening the proposed anti-invasion mechanism.

   Evidence Co-IP, luciferase reporter, ChIP, EMSA, Transwell assays, and in vivo/in vitro gain/loss-of-function in cancer cells

   PMID:33718512 PMID:33788346

   Open questions at the time

   • Multiple parallel signaling outputs not reconciled into one model
   • Relationship between cancer signaling roles and axonemal function unclear
   • VPS33B interaction not reciprocally validated across studies
6. 2020 High

   Defined the core mechanistic role of CFAP45 as an axonemal AMP-binding partner of adenylate kinase AK8 that sustains adenine nucleotide homeostasis for dynein-driven microtubule sliding and ciliary/flagellar beating.

   Evidence In vitro AMP-binding assay, structural modelling, proteomics of CFAP45-deficient cilia, and Cfap45 knockout mouse with microtubule sliding rescue by AMP/ADP

   PMID:33139725

   Open questions at the time

   • Structural model of the AK8 interface not experimentally resolved
   • Stoichiometry and exact placement within the axoneme not defined
   • Does not connect to the cancer signaling roles reported separately
7. 2023 Medium

   Resolved CFAP45's static axonemal position and showed it is required for cilia stability, linking its loss to organ laterality defects, and established CFAP52 as a stabilizing physical partner.

   Evidence Cfap45 morpholino depletion and live confocal imaging in Xenopus LRO cilia; CFAP52-CFAP45 Co-IP and Cfap52 knockout mouse with sliding assay

   PMID:37172641 PMID:37236356

   Open questions at the time

   • Molecular basis of how CFAP45 confers cilia stability is unknown
   • Mechanism by which CFAP52 maintains CFAP45 levels not defined
   • Single-lab depletion studies

• How the axonemal nucleotide-homeostasis function and the reported cancer-signaling roles of CFAP45 relate, if at all, remains unresolved.
• No study bridges the ciliary/flagellar mechanism and the PI3K/AKT/Wnt signaling reports
• No human disease-causing mutation directly demonstrated in the timeline
• Direct binding partners beyond AK8/CFAP52/VPS33B not mapped