Table 2.
Primary proteins in the glycogen granule proteome and their interactions
List of main human glycosome-associated proteins as identified by name and UNIPROT identifier (ID) as well as primary interactions relevant to glycogen metabolism. Protein–protein interactions were derived from databases within UniProt (uniprot.org) (80), mainly The Biological General Repository for Interaction Datasets (BioGrid) (81) and the Protein Interaction Database and Analysis System (IntAct) (82). Abbreviations used are as follows: AMPK, 5′-AMP-activated protein kinase; EMP2A, laforin; GBE, branching enzyme; GDE, debranching enzyme; GN, glycogenin; GP, glycogen phosphorylase; GS, glycogen synthase; PhK, phosphorylase kinase; PP1, protein phosphatase; STDB1, starch-binding domain-containing protein 1; TRIM7, tripartite motif-containing protein.
| Protein | Role | UniProt ID | Key glycogen-related interactions |
|---|---|---|---|
| Glycogenin (GN) | Initiation | P46976 (GN1, muscle) O15488 (GN2, liver) | GS, AMPK, GBE, GP, STBD1, PP1 (PPP1R3C, PPP1CA, PPP1R5), TRIM7 |
| Tripartite motif-containing protein (TRIM7, GNIP) | Initiation, regulation | Q9C029 (TRIM7) | GN |
| Glycogen synthase (GS) | Synthesis | P13807 (GS1, muscle) P54840 (GS2, liver) | GN, AMPK, GBE, PP1 (PP1R3B, PPP1R3C, PPP1CA), STBD1, KAPCA, CSK21, MAPKAPK2, GSK3, PAST, laforin, MLP3B/3C, DYRK |
| Glycogen branching enzyme (GBE) | Synthesis | Q04446 | GP, GS, GN, STBD1, GBE, VAPA |
| Glycogen phosphorylase (GP) | Degradation | P11217 (PYGM, muscle) P11216 (PYGB, brain) P06737 (PYGL, liver) | AMPK, PKC, GBE1, PP2, MAPKAPK2, PP1 |
| Glycogen debranching enzyme (GDE, AGL) | Degradation | P35573 | AMPK, PP1, malin, AMPK, STBD1 |
| Malin (E3 ubiquitin-protein ligase NHLRC1) | Ubiquitin ligase | Q6VVB1 | Laforin, GS, PP1, GDE, AMPK |
| 5′-AMP-activated protein kinase (AMPK) | Kinase | P54646 (α2) Q9Y478 (β1) O43741 (β2) | Laforin, PP1 (PPP2CA, PPP2R1B), PHKG2, CAMK, GN |
| Laforin (EPM2A) | Carbohydrate phosphatase, ubiquitin ligase | O95278 | AMPK, PP1 (PPP1R3C, PPP1R3D), GSK3B, STBD1, GS, malin, |
| Protein phosphatase I (PP1) and targeting subunits | Phosphatase, main regulatory and catalytic subunits | PP1 | AMPK, laforin, GSK3B, GN, GS |
| Q16821 (PPP1R3A, GM) Q86X16 (PPP1R3B, GL) Q0VCR4 (PPP1R3C, PTG) O95685 (PPP1R3D, PPP1R6) P67775 (PPP2CA) | |||
| P62136 (PPP1CA) P30154 (PPP2R1B) | |||
| Phosphorylase kinase (PhK) | Kinase | P15735 (γ, liver, testis) Q16816 (γ, muscle) | AMPK, PP1 (PPP1R3B), GP |
| Starch-binding domain- containing protein 1 (STBD1) | Cargo receptor for glycogen | O95210 | GDE, GBE, PP1, malin, GN, GS, AMPK, GP, MLP3B/3C |