SPKW Autophagy Subproject

SPKW Autophagy Subproject

Parent project: SPKW.md

Overview

This subproject identifies human proteins annotated to "autophagy" (GO:0006914) where the only evidence comes from UniProt Keywords mapping (GO_REF:0000043).

Summary Statistics

Status

Key Concern

The UniProt "Autophagy" keyword may be applied to:
1. Core autophagy machinery (ATG proteins, VPS proteins) - LEGITIMATE
2. Proteins that regulate autophagy (kinases, transcription factors) - may be over-annotation
3. Proteins that are substrates of autophagy (cargo receptors, aggregates) - may be over-annotation
4. Proteins whose loss affects autophagy flux through pleiotropic effects

Pilot Batch for Review

Gene UniProt Description Core Function (confirmed) Status
ABL1 P00519 Tyrosine-protein kinase ABL1 Non-receptor tyrosine kinase (cytoskeleton, DNA damage) OVER-ANNOTATION
BCL2 P10415 Apoptosis regulator Bcl-2 Anti-apoptotic (MOMP inhibition) OVER-ANNOTATION
FOXO1 Q12778 Forkhead box protein O1 Transcription factor (metabolism) OVER-ANNOTATION
LRRK2 Q5S007 Leucine-rich repeat kinase 2 Ser/Thr kinase + GTPase (Rab phosphorylation) OVER-ANNOTATION

Result: 4/4 genes (100%) are OVER-ANNOTATED

Note: HDAC6 was initially included but removed from this analysis - it has corroborating evidence (IGI for GO:0061734 type 2 mitophagy from PMID:20457763), so it does not meet the SPKW-only criteria. The HDAC6 gene review was retained separately.

Criteria for Legitimate Autophagy Annotation

A legitimate annotation requires evidence that the gene:
1. Has an evolved function in autophagosome formation/maturation
2. Is part of the core autophagy machinery (ATG proteins, PI3K complex, LC3 system)
3. Functions as a selective autophagy receptor as its primary function
4. Has direct physical role in autophagy pathway (e.g., cargo trafficking to autophagosome)

NOT legitimate if:
- Regulates autophagy via upstream signaling (kinases, TFs)
- Is degraded by autophagy (substrate)
- Loss causes autophagy defects through pleiotropic effects

Detailed Analysis - Autophagy Pilot

ABL1 (P00519) - Tyrosine-protein kinase ABL1

Core function: Non-receptor tyrosine kinase (EC 2.7.10.2) with SH2-SH3-kinase architecture. Functions in DNA damage response (DDR), cytoskeletal dynamics (F-actin binding), and cell signaling. Famously drives CML when fused to BCR.

Why OVER-ANNOTATION:
- Deep research is entirely about tyrosine kinase activity: DDR, cytoskeleton, BCR-ABL in leukemia, allosteric regulation
- No mention of autophagy in deep research
- Core function is tyrosine phosphorylation of diverse substrates (YAP1, HK2, RAD51)
- Any autophagy effects would be through signaling cascades, not direct participation

BCL2 (P10415) - Apoptosis regulator Bcl-2

Core function: Anti-apoptotic regulator that prevents mitochondrial outer membrane permeabilization (MOMP). BH1-4 domains form hydrophobic groove that sequesters BH3-only proteins (BIM, PUMA) and restrains BAX/BAK.

Why OVER-ANNOTATION:
- Core evolved function is clearly apoptosis regulation
- BCL2 does interact with BECN1 (Beclin-1) and can regulate autophagy
- However, this is a regulatory interaction - BCL2's evolved function is to inhibit apoptosis, and its autophagy regulation is through the same BH3-groove mechanism
- BCL2 didn't evolve TO regulate autophagy - it evolved to regulate apoptosis, and BECN1 happens to have a BH3 domain
- The annotation "autophagy" implies direct participation, not regulatory crosstalk

FOXO1 (Q12778) - Forkhead box protein O1

Core function: Forkhead transcription factor that binds 5′-TTGTTTAC-3′ consensus. Regulated by insulin/PI3K/AKT signaling. Primary functions in gluconeogenesis (activates PCK1, G6PC), oxidative stress, and metabolic homeostasis.

Why OVER-ANNOTATION:
- Deep research is about metabolic control and transcription factor function
- FOXO1 can transcriptionally activate autophagy genes as one of its many target gene programs
- But FOXO1's evolved function is as a metabolic transcription factor, not as autophagy machinery
- This is similar to annotating p53 to "apoptosis" - it regulates apoptosis genes but its core function is broader
- Transcriptional regulation of autophagy ≠ direct function in autophagy

LRRK2 (Q5S007) - Leucine-rich repeat serine/threonine-protein kinase 2

Core function: Dual enzyme with Ser/Thr kinase (EC 2.7.11.1) and GTPase (EC 3.6.5.-) activities. Primary substrates are Rab GTPases (Rab10 Thr73, Rab8, Rab12). Regulates endolysosomal trafficking and ciliogenesis. Linked to Parkinson's disease.

Why OVER-ANNOTATION:
- Deep research is about Rab phosphorylation and endolysosomal trafficking
- LRRK2 affects the lysosomal system (LYTL - lysosomal tubulation/sorting)
- While autophagy ultimately requires lysosomes, LRRK2's evolved function is Rab-mediated membrane trafficking
- Autophagy defects from LRRK2 mutations are downstream effects of impaired endolysosomal trafficking
- Core function is Rab phosphorylation for trafficking, not autophagosome biogenesis

Legitimate Genes Identified

Three genes were found to have legitimate autophagy annotations:

DRAM1 - Lysosomal Membrane Protein

Core function: Lysosomal transmembrane protein that promotes autophagy.

Why LEGITIMATE:
- Localized to lysosomes and functions in autophagic flux
- Stabilizes VAMP8 to promote autophagosome-lysosome fusion
- p53-inducible as part of autophagy/cell death decisions
- Direct role in autophagy pathway

DRAM2 - Lysosomal Membrane Protein

Core function: Lysosomal transmembrane protein similar to DRAM1.

Why LEGITIMATE:
- Functions in autophagy via lysosomal membrane localization
- Promotes autophagic flux
- Part of DRAM family with established autophagy roles

DAP - Death-Associated Protein

Core function: mTORC1 substrate that regulates autophagy.

Why LEGITIMATE:
- Functions as a negative regulator of autophagy
- Direct mTORC1 substrate involved in autophagy control
- Evolved function in autophagy regulation pathway

Key Findings

  1. Autophagy keyword too broadly applied:
  2. Applied to kinases that phosphorylate autophagy components
  3. Applied to transcription factors that regulate autophagy genes

  4. Applied to proteins with downstream effects on autophagy

  5. Result: 11/14 genes are over-annotated (79%)

  6. Pattern similar to apoptosis:

  7. Regulatory crosstalk ≠ direct function
  8. Transcriptional regulation ≠ participation
  9. Downstream effects ≠ evolved function