PYCARD (ASC) review notes

Provenance note: provider deep research for this gene FAILED (Falcon returned HTTP 402
Payment Required; Perplexity is not configured). This file is a manual literature synthesis
built from the UniProt record (Q9ULZ3), the cached publications under publications/, and a
targeted web search (for the Dock2 confound, below). It replaces the provider deep-research
report. No *-deep-research-<provider>.md file exists for this gene.

Identity and domain architecture

• Human PYCARD, UniProt Q9ULZ3, 195 aa. Also called ASC (apoptosis-associated speck-like
  protein containing a CARD) and TMS1 (target of methylation-induced silencing 1).
• Two death-fold domains joined by a flexible linker: N-terminal pyrin domain (PYD, residues
  1-91) and C-terminal CARD (residues 107-195) (UniProt FT DOMAIN). No catalytic domain.
• First identified as a protein that aggregates into a "speck" during apoptosis of HL-60 cells
  PMID:10567338.
• PANTHER places it in PTHR46985 (NLRP1 family name) subfamily SF2 because it shares PYD and
  CARD domains with NLRP1/CARD8; it has no NACHT or LRR domain.

Core function: bipartite adaptor of ASC-dependent inflammasomes

• ASC bridges sensor and caspase-1 through homotypic interactions
  PMID:24630722.
• Two nucleation-polymerization steps: sensors nucleate ASC PYD filaments; clustered ASC CARDs
  nucleate caspase-1 CARD filaments, causing proximity-induced activation
  [PMID:24630722 "Activated AIM2 and NLRP3 nucleate PYD filaments of ASC, which, in turn,
  cluster the CARD of ASC."; "ASC thus nucleates CARD filaments of caspase-1, leading to
  proximity-induced activation."].
• NLRP3 PYD filaments seed unidirectional ASC elongation
  PMID:35559676; the active NLRP3
  disc presents a PYD filament that recruits ASC PYD
  PMID:36442502.
• NMR: ASC PYD self-associates and binds NLRP3 PYD via equivalent surfaces
  PMID:27432880. PYD self-association depends
  on charged residues on helices 2-4 PMID:15641782.
• Pyroptosome / speck: one per cell, made of oligomerized ASC dimers, recruits and activates
  caspase-1 [PMID:17599095 "The pyroptosome is largely composed of oligomerized ASC dimers.";
  "Only one distinct pyroptosome in each stimulated cell is formed, which rapidly recruits and
  activates caspase-1 resulting in pyroptosis and the release of the intracellular
  proinflammatory cytokines."].
• Inflammasomes using ASC:
• NLRP1 PMID:12191486; immunodepletion of Pycard abolishes caspase activation and proIL-1b processing
  PMID:12191486. In a purified NLRP1 system ASC enhances but is not
  required PMID:17349957.
• NLRP3 PMID:15030775; NLRP3-driven IL-1b secretion requires ASC
  PMID:15020601.
• Pyrin/MEFV [PMID:16037825 "pyrin, like cryopyrin, can also assemble an inflammasome
  complex with ASC and procaspase-1 leading to ASC oligomerization, caspase-1 activation and
  interleukin-1beta processing"; PMID:17964261].
• AIM2 [PMID:19158675 "AIM2 as a new receptor for cytoplasmic DNA, which forms an
  inflammasome with the ligand and ASC to activate caspase-1"; PMID:19158676; PMID:19158679].
• IFI16 (nuclear, KSHV) PMID:21575908.
• NLRP6 [PMID:30674671 "NLRP6 PYD alone is able to self-assemble into filamentous structures
  ... and can recruit the ASC adaptor using PYD-PYD interactions"; PMID:34678144
  "Recruitment of ASC via helical assembly solidifies NLRP6 condensates, and ASC further
  recruits and activates caspase-1."].
• NLRC4: NAIP-NLRC4 can activate caspase-1 directly via its own CARD; ASC is dispensable for
  pyroptosis there but contributes to cytokine processing PMID:25879286. NLRC4 and NLRP3 co-occupy one ASC ring in
  Salmonella-infected macrophages PMID:24803432.
• Nuclear-to-cytosol relocation is required for inflammasome function
  [PMID:19234215 "ASC localized primarily to the nucleus in resting human
  monocytes/macrophages"; "cytosolic localization of ASC is essential for inflammasome
  function"]. PML retains ASC in the nucleus PMID:24407287.
• Regulation: K63 ubiquitination at K174 by TRAF3 downstream of MAVS needed for specks
  PMID:25847972; Syk phosphorylation at Y146/Y187 PMID:25605870; PYD-only proteins
  POP1/POP2/POP3 compete for ASC [PMID:12656673; PMID:17178784; PMID:24531343].
• Released ASC specks act extracellularly to propagate inflammation
  PMID:24952504.
• Noncanonical: ASC is recruited with MALT1-caspase-8 into the dectin-1/CARD9 scaffold for
  caspase-8-mediated pro-IL-1b processing PMID:22267217.

Downstream outputs

• IL-1b/IL-18 maturation and pyroptosis via caspase-1 and gasdermin D [PMID:29196474;
  PMID:26611636 noting "ASC is not essential for GSDMD to function" but "The induction of
  apoptosis required NLRP3 or other inflammasome receptors and ASC"].

Inflammasome-independent and apoptotic roles (secondary, context-dependent)

• Apoptosis: originally pro-apoptotic; caspase-8-dependent apoptosis PMID:12646168,
  caspase-9 PMID:11103777, Bid-dependent in type II cells PMID:16964285, Bax adaptor in
  p53 pathway PMID:14730312, though
  ASC-Bax colocalization was not reproduced PMID:16964285. TMS1 is silenced by methylation in breast cancers PMID:11103777. These apoptotic activities are mostly from overexpression systems.
• NF-kB modulation: dual/context-dependent — can activate PMID:11786556 or inhibit at the
  IKK level PMID:12486103. Direction is inconsistent across studies.
• Cytokine/chemokine induction via MAPK: ASC suppresses DUSP10/MKP5, raising ERK/JNK
  phosphorylation and chemokine output independently of caspase-1/IL-1b
  PMID:21487011. P. gingivalis cytokine induction (IL-6, IL-8,
  IL-10, TNF) needs ASC PMID:16982856.

IMPORTANT confound for the adaptive-immunity / Dock2 / actin / T-cell / DC annotations

The dendritic-cell maturation, T-cell activation/migration, phagocytosis, macropinocytosis,
and actin-polymerization annotations trace to work on ASC-deficient mice reporting a
cell-intrinsic, inflammasome-independent role of ASC in controlling Dock2 mRNA stability and
Rac-mediated actin polymerization [PMID:21892172 "ASC shapes adaptive immunity independently
of inflammasomes by modulating Dock2-dependent Rac activation and actin polymerization in DCs
and lymphocytes."; "ASC-deficient mice showed defective antigen presentation by dendritic
cells (DCs) and lymphocyte migration due to impaired actin polymerization mediated by the
small GTPase Rac."]. The SAME authors subsequently published an Addendum reporting this is a
passenger mutation artifact: the Dock2 defect is present in only a subset of ASC-deficient
mouse lines, i.e. a flanking/strain confound rather than a function of ASC
PMID:22905357. Consequently the Dock2/Rac/actin/DC/T-cell cascade of GO annotations is not safe to
treat as a direct ASC function. Annotations derived from PMID:22732093 (the human DC paper
using RNAi, not the Dock2 mouse) are on firmer ground but still describe a secondary,
non-core role. These are handled as KEEP_AS_NON_CORE / MARK_AS_OVER_ANNOTATED / UNDECIDED, not
as core functions, and not REMOVE (experimental annotations whose full text was not fully
read).

Subcellular localization

• Core: cytosol/cytoplasm (resting), relocating to a single perinuclear speck/inflammasome on
  activation [PMID:11103777; PMID:12191486; PMID:15030775]. Nucleus is a genuine resting
  location in monocytes PMID:19234215. ER/mitochondria redistribution on NLRP3 activation
  PMID:21124315. Golgi membrane only under HRSV infection PMID:23229815.
• Extracellular region / granule-lumen annotations are Reactome neutrophil-degranulation
  pathway memberships, not a primary ASC location (secondary).

Consistency with NLRP3 review

Keep terminology consistent with genes/human/NLRP3: NLRP3 is the sensor/activator that
nucleates; ASC is the adaptor that polymerizes and recruits caspase-1. Core MF for ASC =
signaling adaptor activity (GO:0035591); NLRP3 also carries signaling adaptor activity for its
own nucleation step but ASC is the canonical adaptor. ASC also carries
cysteine-type endopeptidase activator activity (GO:0140608) because its CARD filament directly
drives procaspase-1 proximity-induced autoactivation. Avoid "protein binding".

2026-11-03 ORGANELLES batch 4 (mitochondrion rows)

Rows: GO:0005739 EXP (PMID:21124315), IDA (PMID:14730312), IEA (GO_REF:0000044, SL-0173),
all located_in, all KEEP_AS_NON_CORE. No sub-compartment or MAM rows.

Checks:
- UniProt Q9ULZ3 curates Mitochondrion to the two direct papers
(ECO:0000269|PubMed:14730312, PubMed:21124315), so the IEA is derived from them.
- PMID:21124315 (abstract-only): activation-induced redistribution to perinuclear ER and
mitochondria clusters PMID:21124315.
Imaging cannot separate mitochondrion from ER contacts; no MAM marker.
- PMID:14730312 (abstract-only): overexpressed ASC co-localizes with Bax
PMID:14730312.
- No presequence or TM; MitoCarta3.0 does not list PYCARD; HPA "Nucleoplasm (Supported)".

Outcome: actions unchanged (KEEP_AS_NON_CORE), reasons record the check. Transient,
stimulus-dependent recruitment of a soluble adaptor, not an outer-membrane location
(TRAF3/BRAF precedent); stays at the root. The IDA row's quote was about Bax translocation;
added the sentence about ASC's own colocalization. EXP row given a supporting quote.

2026-11-05 ORGANELLES ER batch 3 (endoplasmic reticulum rows)

Rows: GO:0005783 EXP (PMID:21124315) and IEA (GO_REF:0000044, SL-0095), both located_in,
both KEEP_AS_NON_CORE. No ER sub-compartment or MAM rows.

Checks:
- UniProt Q9ULZ3 curates "Endoplasmic reticulum {ECO:0000269|PubMed:21124315}" only, so the IEA
derives from the EXP row.
- PMID:21124315 (abstract-only): PMID:21124315.
Imaging of organelle clusters, no ER-specific marker or fractionation in the abstract.
- Soluble PYD-CARD adaptor: no signal peptide, TM or retention motif.

Outcome: actions unchanged (KEEP_AS_NON_CORE); reasons record the check. Recruited pool on the
cytosolic face, stays at the root (A1CF, BRSK2 precedent), consistent with the batch 4
mitochondrion rows. IEA row given a UniProt quote.