FRY

FRY (Protein furry homolog) is an evolutionarily conserved scaffold protein that coordinates multiple mitotic regulatory pathways to ensure accurate cell division. It scaffolds the MST2→NDR1 kinase activation complex by binding both NDR1 and MOB2, synergistically activating NDR1 kinase activity required for proper chromosome alignment at metaphase (PMID:19327996). FRY also facilitates Aurora A–mediated phosphorylation of Plk1 at Thr-210 through CDK1-dependent binding to Plk1's polo-box domain, maintaining bipolar spindle integrity (PMID:22753416), and promotes α-tubulin acetylation on spindle microtubules by directly binding and inhibiting the deacetylase SIRT2 (PMID:23886946). In vivo, FRY is required for mammary lobuloalveolar development during pregnancy and suppresses breast cancer cell proliferation in part through Hippo/YAP pathway activation (PMID:31824855).

1. 2009 High

   Establishing FRY as a mitotic scaffold resolved how the conserved MST–NDR signaling cascade is organized in mammalian cells: FRY bridges NDR1 and MOB2, synergistically activating NDR1 downstream of MST2 to ensure chromosome alignment.

   Evidence Co-IP, in vitro kinase assays, siRNA epistasis rescue with constitutively active NDR1 in HeLa cells

   PMID:19327996

   Open questions at the time

   • Structural basis of FRY–NDR1–MOB2 ternary complex unknown
   • Whether FRY scaffolds NDR2 similarly is untested
   • Regulation of FRY recruitment to the spindle not defined
2. 2010 Medium

   Drosophila studies demonstrated that the Fry–Trc (NDR kinase) interaction is conserved and dynamically regulated, with Fry directing polarized cell morphogenesis independently of the Wts/Yorkie branch of Hippo signaling.

   Evidence Co-IP from wing disc lysates; live GFP imaging showing Fry mobility and tip accumulation; genetic epistasis separating Trc/Fry from Wts/Yorkie in wing cells

   PMID:20211163 PMID:20406475

   Open questions at the time

   • Whether the transient nature of Fry–Trc interaction is phosphorylation-regulated remains unclear
   • Direct transcriptional targets downstream of Fry/Trc not identified in mammals
3. 2012 High

   Identification of FRY as a CDK1-phosphorylation-dependent adaptor bridging Aurora A to Plk1 revealed a second mitotic axis through which FRY ensures bipolar spindle formation, explaining why FRY depletion causes centrosome splitting and multipolar spindles.

   Evidence Co-IP of FRY with Plk1 and Aurora A; site-directed mutagenesis of FRY Thr-2516; in vitro kinase assays; siRNA depletion with spindle phenotype analysis

   PMID:22753416

   Open questions at the time

   • Whether FRY simultaneously scaffolds NDR1 and Plk1 complexes or these are mutually exclusive is unknown
   • No structural model of FRY–PBD interaction exists
4. 2013 High

   Discovery that FRY directly binds and inhibits the tubulin deacetylase SIRT2 established a third mitotic function — promotion of spindle microtubule acetylation — mechanistically distinct from its kinase-scaffolding roles.

   Evidence Cell-free deacetylase inhibition assay with N-terminal FRY fragment; Co-IP; siRNA depletion with chemical rescue by SIRT2 inhibitor AGK2

   PMID:23886946

   Open questions at the time

   • Functional consequence of reduced spindle acetylation for chromosome segregation fidelity not directly tested
   • Whether SIRT2 inhibition and NDR1 scaffolding are coordinated through the same FRY molecule is unknown
5. 2013 Medium

   Genetic linkage and expression analysis identified FRY as a candidate mammary carcinoma susceptibility gene, with reduced expression in rat mammary tumors and human breast cancer cell lines, motivating investigation of FRY's tumor-suppressive role.

   Evidence Backcross linkage mapping (LOD ~8.6) in rat; SNP analysis; RT-PCR expression profiling in mammary tumors and human cell lines

   PMID:24023717

   Open questions at the time

   • Causative role of identified SNPs not functionally validated
   • Mechanism linking FRY loss to tumor susceptibility not established in this study
6. 2019 Medium

   Conditional knockout and gain-of-function experiments demonstrated that FRY is required for mammary lobuloalveolar development during pregnancy and suppresses breast cancer cell proliferation through Hippo/YAP pathway activation, linking its kinase-scaffolding function to tissue-level growth control.

   Evidence Cre-loxP mammary-specific Fry knockout mice with histological analysis; ectopic FRY expression in MDA-MB-231 and BT474 with proliferation assays and RNA-seq

   PMID:31824855

   Open questions at the time

   • Direct FRY–YAP biochemical interaction not demonstrated
   • Whether tumor suppression depends on NDR1 scaffolding versus other FRY functions is untested
   • Relevance to human breast cancer patients not established

• How FRY integrates its three known mitotic functions (NDR1 scaffolding, Plk1 activation, SIRT2 inhibition) temporally during mitotic progression, and whether its tumor-suppressive activity in mammary tissue operates through these same mechanisms, remains unresolved.
• No structural or cryo-EM model of FRY or its complexes exists
• Post-translational regulation of FRY beyond CDK1 phosphorylation at Thr-2516 is unexplored
• Whether FRY loss contributes to aneuploidy in cancer through its mitotic functions is untested