Affinage

WHAMM

WASP homolog-associated protein with actin, membranes and microtubules · UniProt Q8TF30

Length
809 aa
Mass
90.9 kDa
Annotated
2026-06-11
17 papers in source corpus 14 papers cited in narrative 13 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 6/6 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

WHAMM is a Wiskott-Aldrich Syndrome protein family nucleation-promoting factor that activates the Arp2/3 complex to drive branched actin polymerization in service of membrane remodeling, autophagy, and intrinsic apoptosis (PMID:26096974, PMID:26291929, PMID:28720660). Its central coiled-coil region binds the outer surface of microtubule protofilaments through a short MT-binding peptide motif that adopts distinct conformations in the free and MT-bound states; this engagement exposes the N-terminal membrane-binding domain to recruit and tubulate vesicles while simultaneously masking the C-terminal WCA domain to suppress actin nucleation (PMID:23027905, PMID:28351611). WHAMM is recruited to membranes through phosphoinositide engagement—PI(3)P at nascent autophagosomes and PI(4,5)P2 at autolysosomes—and through the GTP-bound G-protein Rab1, which paradoxically recruits the nucleation machinery to tubulovesicular structures while dampening its Arp2/3-dependent actin assembly (PMID:26823012, PMID:31420534, PMID:28720660). Functionally, WHAMM directs Arp2/3 activity at the ER to nucleate actin comet tails that build autophagosomes, controls autophagosomal membrane closure and cargo receptor recruitment, and drives actin-scaffold-dependent tubulation required for autophagic lysosome reformation; its loss impairs LC3 lipidation, autophagic flux, and clearance of ubiquitinated aggregates (PMID:26096974, PMID:26291929, PMID:31420534, PMID:28720660, PMID:38598293). Independently, WHAMM promotes the intrinsic mitochondrial apoptosis pathway in an Arp2/3- and p53-dependent manner, enhancing mitochondrial permeabilization, cytochrome c release, and caspase activation, with RhoD opposing this death pathway (PMID:33872315, PMID:40138314). A WHAMM founder mutation in patient cells produces cytoskeletal irregularities and severe autophagy defects rescued by wild-type WHAMM, and Whamm-knockout mice show LC3 accumulation and proximal tubule structural abnormalities (PMID:28720660, PMID:38598293).

Mechanistic history

Synthesis pass · year-by-year structured walk · 9 steps
  1. 2012 High

    Resolving how WHAMM couples microtubules to membrane remodeling established that its coiled-coil binds tubulin while its termini are conformationally gated—MT binding exposes the membrane-binding domain and silences actin nucleation.

    Evidence Cryo-EM of WHAMM on microtubules with in vitro binding assays and domain mutagenesis

    PMID:23027905

    Open questions at the time
    • Did not define the in vivo trigger that releases the WCA domain for nucleation
    • Physiological setting of MT-templated vesicle tubulation not established
  2. 2012 Medium

    Identifying WHAMM at the meiotic spindle extended its role beyond interphase trafficking to actin- and microtubule-dependent asymmetric division.

    Evidence Immunostaining and siRNA microinjection in mouse oocytes with nocodazole/taxol treatment

    PMID:23160625

    Open questions at the time
    • No molecular mechanism linking WHAMM to spindle migration
    • Whether Arp2/3 activation underlies the actin cap defect not tested
  3. 2015 High

    Connecting WHAMM to autophagosome biogenesis showed it directs Arp2/3-mediated actin comet tails at the ER, defining a cytoskeletal driver of early autophagy.

    Evidence Live-cell imaging, siRNA knockdown, Arp2/3-interaction mutagenesis, and pharmacological actin/Arp2/3 inhibition across two companion papers

    PMID:26096974 PMID:26291929

    Open questions at the time
    • How WHAMM is initially targeted to the ER/autophagosome interface not resolved here
    • Relationship between comet-tail force and membrane shaping not quantified
  4. 2016 High

    Defining Rab1 as an upstream recruiter clarified that a Rab GTPase positions WHAMM on tubulovesicular structures yet restrains its actin-nucleating output.

    Evidence Co-localization in fibroblasts, in vitro prenylated-Rab1 binding to N-terminal WHAMM, and actin assembly assays

    PMID:26823012

    Open questions at the time
    • Signal relieving Rab1-mediated inhibition unknown
    • Whether Rab1 regulation operates during autophagy specifically not tested
  5. 2017 High

    Mapping phosphoinositide and tubulin binding plus patient-cell complementation established WHAMM's PI(3)P-dependent membrane recruitment and causal role in human autophagy.

    Evidence Cryo-EM of the MT-binding motif with cross-linking MS; patient cell complementation, PI(3)P binding, LC3 lipidation and aggregate-clearance assays

    PMID:28351611 PMID:28720660

    Open questions at the time
    • Identity of the disease and full genotype-phenotype relationship not detailed in the corpus
    • How PI(3)P binding is coordinated with Arp2/3 activation unresolved
  6. 2019 High

    Demonstrating WHAMM in autophagic lysosome reformation showed its membrane targeting is lipid-context-specific—PI(4,5)P2 at autolysosomes—driving actin-scaffold tubulation distinct from biogenesis.

    Evidence WHAMM knockout, PI(4,5)P2 lipid-binding assay, and live imaging of autolysosome tubulation

    PMID:31420534

    Open questions at the time
    • How WHAMM switches between PI(3)P and PI(4,5)P2 membranes not defined
    • Force-generation mechanism for tubulation not reconstituted
  7. 2021 Medium

    Linking WHAMM to intrinsic apoptosis revealed an Arp2/3- and p53-dependent role in mitochondrial permeabilization and caspase activation, with RhoD as an opposing regulator.

    Evidence WASP-family gene inactivation (CRISPR/siRNA), caspase and cytochrome c release assays, live imaging, and RhoD epistasis

    PMID:33872315

    Open questions at the time
    • How actin filaments mechanistically promote mitochondrial permeabilization unclear
    • RhoD-WHAMM physical interaction in death context not structurally defined
  8. 2024 High

    In vivo knockout established WHAMM's requirement for autophagosomal membrane closure and cargo receptor recruitment, with physiological consequences in kidney proximal tubule function.

    Evidence Whamm knockout mice with LC3 lipidation flux assays and membrane closure assays in cell lines

    PMID:38598293

    Open questions at the time
    • Molecular mechanism of closure versus cargo recruitment not separated
    • Tissue specificity of the phenotype not fully explained
  9. 2025 Medium

    Extending WHAMM's death-promoting role to disease, actin-mediated cytochrome c release and ASC speck formation were connected to experimental kidney injury treatable by actin inhibition.

    Evidence Whamm-deletion mouse disease models (cisplatin, folic acid, UUO), cytochrome c and ASC speck assays, pharmacological actin inhibition

    PMID:40138314

    Open questions at the time
    • Specificity of actin inhibitors for WHAMM-driven pathway not established
    • Relationship between WHAMM's autophagy and apoptosis functions in tubule cells unresolved

Open questions

Synthesis pass · forward-looking unresolved questions
  • How WHAMM's competing membrane-targeting, microtubule-binding, Rab1-inhibition, and Arp2/3-activation states are switched to select between autophagy, lysosome reformation, and apoptosis remains unresolved.
  • No unified regulatory model integrating the conformational gating, phosphoinositide selection, and Rab/Rho G-protein inputs
  • Mechanism partitioning pro-autophagy versus pro-apoptotic WHAMM activity unknown

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0008092 cytoskeletal protein binding 3 GO:0008289 lipid binding 2 GO:0140096 catalytic activity, acting on a protein 2 GO:0060089 molecular transducer activity 1
Localization
GO:0005739 mitochondrion 2 GO:0005856 cytoskeleton 2 GO:0005764 lysosome 1 GO:0005783 endoplasmic reticulum 1
Pathway
R-HSA-9612973 Autophagy 4 R-HSA-5357801 Programmed Cell Death 2 R-HSA-5653656 Vesicle-mediated transport 2
Partners
ACTBACTR2/ACTR3 (ARP2/3 COMPLEX)RAB1RHODTUBB/TUBULIN

Evidence

Reading pass · 13 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2012 WHAMM binds to the outer surface of microtubule protofilaments via a novel interaction between its central coiled-coil region and tubulin heterodimers; upon MT binding, the N-terminal membrane-binding domain is exposed at the MT periphery to recruit and remodel vesicles into tubular structures, while MT binding simultaneously masks the C-terminal WCA domain and prevents actin nucleation activity. Cryo-electron microscopy, biophysical and biochemical approaches (in vitro binding assays, domain mutagenesis) The Journal of cell biology High 23027905
2017 WHAMM interacts with αβ-tubulin through a small peptide motif (MT-binding motif, MBM) within its MT-binding domain; cryo-EM reconstruction revealed the atomic-level arrangement of MBM around MTs, and chemical cross-linking/mass spectrometry confirmed a conformational switch of the MBM between the non-MT-bound and MT-bound states. Cryo-electron microscopy, chemical cross-linking, mass spectrometry Journal of molecular biology High 28351611
2016 Active Rab1 (GTP-bound) recruits WHAMM to dynamic tubulovesicular structures and a prenylated active form of Rab1 binds directly to an N-terminal domain of WHAMM in vitro; paradoxically, Rab1 binding inhibits WHAMM-mediated Arp2/3-dependent actin assembly, representing a strategy where a Rab G-protein recruits the nucleation machinery but dampens its activity. Co-localization in fibroblasts, in vitro direct binding assay (prenylated Rab1 pulldown with N-terminal WHAMM domain), actin assembly assay Molecular biology of the cell High 26823012
2015 WHAMM directs Arp2/3 complex activity at the ER to drive autophagosome biogenesis via an actin comet-tail mechanism; WHAMM puncta colocalize and comigrate with autophagy markers LC3, DFCP1, and p62, and knockdown of WHAMM or mutagenesis blocking its interaction with Arp2/3 complex reduces autophagosome size and number. Live-cell imaging, siRNA knockdown, Arp2/3-interaction mutagenesis, pharmacological inhibition of actin polymerization and Arp2/3 complex Current biology : CB High 26096974 26291929
2019 WHAMM is required for autophagic lysosome reformation (ALR): it is recruited to the autolysosome membrane through specific binding to PI(4,5)P2, then promotes assembly of an actin scaffold on the autolysosome surface to drive tubulation. WHAMM knockout causes accumulation of enlarged autolysosomes during prolonged starvation. WHAMM knockout, lipid-binding assay (PI(4,5)P2 interaction), live-cell imaging of autolysosome tubulation Nature communications High 31420534
2017 WHAMM binds to PI(3)P and promotes actin nucleation at nascent autophagosomes; patient cells harboring a WHAMM founder mutation show cytoskeletal irregularities and severe autophagy defects, and reintroduction of wild-type WHAMM restores autophagosomal biogenesis; WHAMM inactivation in healthy cells inhibits LC3 lipidation and clearance of ubiquitinated aggregates. Patient cell complementation, WHAMM inactivation (siRNA/mutation), PI(3)P binding assay, LC3 lipidation assay, ubiquitinated aggregate clearance assay Molecular biology of the cell High 28720660
2024 WHAMM and its binding partner the Arp2/3 complex control autophagosomal membrane closure and cargo receptor recruitment in mouse fibroblasts and human proximal tubule cells; loss of WHAMM causes accumulation of lipidated LC3 in kidney tissue and structural abnormalities of the proximal tubule affecting nutrient reabsorption in male knockout mice. WHAMM knockout mice (physiological phenotype), autophagy flux assays (LC3 lipidation), membrane closure assays in cell lines Molecular biology of the cell High 38598293
2021 WHAMM promotes the intrinsic (mitochondrial) apoptosis pathway in a p53-dependent manner, enhancing mitochondrial permeabilization, initiator caspase cleavage, and executioner caspase activation; actin filaments assembled via Arp2/3 complex appear in cytoplasmic territories containing cytochrome c clusters and active caspase-3; RhoD (a WHAMM-interacting G-protein) opposes this cell death pathway. WASP-family gene inactivation (CRISPR/siRNA), caspase cleavage assays, cytochrome c release assay, live-cell imaging, RhoD depletion/deletion epistasis PLoS genetics Medium 33872315
2025 WHAMM controls actin-mediated cytochrome c release from mitochondria and ASC speck formation in kidney tubule cells, connecting WHAMM-driven actin dynamics to cell death pathways; pharmacological inhibition of actin dynamics mitigates kidney disease in cisplatin, folic acid, and UUO experimental models. Genetic deletion of Whamm in mice (disease models), in vitro cell studies (cytochrome c release, ASC speck assay), pharmacological actin inhibition Cell reports Medium 40138314
2012 WHAMM localizes to the meiotic spindle in mouse oocytes (after meiosis resumption, not at GV stage), and depletion by siRNA causes failure of spindle migration, disruption of actin cap formation, asymmetric cytokinesis failure, and decreased first polar body extrusion. Immunostaining, siRNA microinjection in mouse oocytes, nocodazole/taxol treatment Histochemistry and cell biology Medium 23160625
2021 WHAMM co-localizes with the actin cage permeating the meiotic spindle in mouse oocytes; depletion impairs spindle formation, displaces the MTOC, disrupts spindle actin formation, and causes chromosomal aneuploidy and abnormal asymmetric division; BFA treatment disperses WHAMM localization, linking ER-to-Golgi trafficking to WHAMM's spindle function. siRNA knockdown in mouse oocytes, immunofluorescence, brefeldin A (BFA) treatment Cell cycle (Georgetown, Tex.) Medium 33397186
2020 WHAMM's interaction with actin is required for initiation of autophagy; in SETD2-null cells the WHAMM–actin interaction is reduced, leading to autophagy defects; this deficit is rescued by pharmacological induction of actin polymerization (jasplakinolide), indicating that the impaired interaction results from altered actin dynamics rather than direct loss of the SETD2-mediated ActK68me3 mark. Co-immunoprecipitation (WHAMM–actin), SETD2 knockout cells, jasplakinolide rescue, autophagy flux assay Biochemical and biophysical research communications Low 33036756
2024 WHAMM enhances autophagosomal localization of TGF-β1 and promotes autophagic degradation of TGF-β1 in type II alveolar epithelial cells, thereby suppressing TGF-β1-driven EMT; knockdown of WHAMM causes accumulation of TGF-β1 and increased EMT markers in a hyperoxia-induced BPD model. WHAMM knockdown/overexpression, autophagy flux assays, TGF-β1 colocalization with autophagosome markers, EMT marker analysis Journal of cellular physiology Low 39564703

Source papers

Stage 0 corpus · 17 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2010 WASH, WHAMM and JMY: regulation of Arp2/3 complex and beyond. Trends in cell biology 151 20888769
2015 WHAMM Directs the Arp2/3 Complex to the ER for Autophagosome Biogenesis through an Actin Comet Tail Mechanism. Current biology : CB 108 26096974
2019 WHAMM initiates autolysosome tubulation by promoting actin polymerization on autolysosomes. Nature communications 60 31420534
2012 Evolution of the eukaryotic ARP2/3 activators of the WASP family: WASP, WAVE, WASH, and WHAMM, and the proposed new family members WAWH and WAML. BMC research notes 53 22316129
2016 Rab1 recruits WHAMM during membrane remodeling but limits actin nucleation. Molecular biology of the cell 28 26823012
2012 Structural insights into WHAMM-mediated cytoskeletal coordination during membrane remodeling. The Journal of cell biology 28 23027905
2015 WHAMM links actin assembly via the Arp2/3 complex to autophagy. Autophagy 24 26291929
2017 An Amish founder mutation disrupts a PI(3)P-WHAMM-Arp2/3 complex-driven autophagosomal remodeling pathway. Molecular biology of the cell 22 28720660
2012 WHAMM is required for meiotic spindle migration and asymmetric cytokinesis in mouse oocytes. Histochemistry and cell biology 18 23160625
2021 The actin nucleation factors JMY and WHAMM enable a rapid Arp2/3 complex-mediated intrinsic pathway of apoptosis. PLoS genetics 13 33872315
2017 Structural Insights of WHAMM's Interaction with Microtubules by Cryo-EM. Journal of molecular biology 11 28351611
2020 An actin-WHAMM interaction linking SETD2 and autophagy. Biochemical and biophysical research communications 8 33036756
2021 WHAMM is essential for spindle formation and spindle actin polymerization in maturing mouse oocytes. Cell cycle (Georgetown, Tex.) 7 33397186
2024 WHAMM functions in kidney reabsorption and polymerizes actin to promote autophagosomal membrane closure and cargo sequestration. Molecular biology of the cell 4 38598293
2025 The actin and microtubule network regulator WHAMM is identified as a key kidney disease risk gene. Cell reports 2 40138314
2024 WHAMM functions in kidney reabsorption and polymerizes actin to promote autophagosomal membrane closure and cargo sequestration. bioRxiv : the preprint server for biology 1 38328079
2024 WHAMM Inhibits Type II Alveolar Epithelial Cell EMT by Mediating Autophagic Degradation of TGF-β1 in Bronchopulmonary Dysplasia. Journal of cellular physiology 0 39564703

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