PMID- 18308511 OWN - NLM STAT- MEDLINE DCOM- 20080929 LR - 20211203 IS - 0898-6568 (Print) IS - 0898-6568 (Linking) VI - 20 IP - 6 DP - 2008 Jun TI - Pam (Protein associated with Myc) functions as an E3 ubiquitin ligase and regulates TSC/mTOR signaling. PG - 1084-91 LID - 10.1016/j.cellsig.2008.01.020 [doi] AB - The tumor suppressor tuberin, encoded by the Tuberous Sclerosis Complex (TSC) gene TSC2, negatively regulates the mammalian target of rapamycin (mTOR) pathway, which plays a key role in the control of cell growth and proliferation. In addition to naturally occurring mutations, several kinases including Akt, RSK1, and ERK are known to phosphorylate and inactivate tuberin. We demonstrate a novel mechanism of tuberin inactivation through ubiquitination by Pam, a putative RING finger-containing E3 ubiquitin (Ub) ligase in mammalian cells. We show that Pam associates with E2 ubiquitin-conjugating enzymes, and tuberin can be ubiquitinated by Pam through its RING finger domain. Tuberin ubiquitination is independent of its phosphorylation by Akt, RSK1, and ERK kinases. Pam is also self-ubiquitinated through its RING finger domain. Moreover, the TSC1 protein hamartin, which forms a heterodimer with tuberin, protects tuberin from ubiquitination by Pam. However, TSC1 fails to protect a disease-associated missense mutant of TSC2 from ubiquitination by Pam. Furthermore, Pam knockdown by RNA interference (RNAi) in rat primary neurons elevates the level of tuberin, and subsequently inhibits the mTOR pathway. Our results provide novel evidence that Pam can function as an E3 Ub ligase toward tuberin and regulate mTOR signaling, suggesting that Pam can in turn regulate cell growth and proliferation as well as neuronal function through the TSC/mTOR pathway in mammalian cells. FAU - Han, Sangyeul AU - Han S AD - Center for Human Genetic Research, Massachusetts General Hospital, Boston, MA 02114, USA. FAU - Witt, Rochelle M AU - Witt RM FAU - Santos, Tulio M AU - Santos TM FAU - Polizzano, Carolyn AU - Polizzano C FAU - Sabatini, Bernardo L AU - Sabatini BL FAU - Ramesh, Vijaya AU - Ramesh V LA - eng GR - P30 NS045776/NS/NINDS NIH HHS/United States GR - NS45776/NS/NINDS NIH HHS/United States GR - R21 MH079213/MH/NIMH NIH HHS/United States GR - P01 NS024279-120008/NS/NINDS NIH HHS/United States GR - P01 NS024279/NS/NINDS NIH HHS/United States GR - NS24279/NS/NINDS NIH HHS/United States GR - R01 NS052707-03/NS/NINDS NIH HHS/United States GR - R01 NS052707/NS/NINDS NIH HHS/United States GR - R21 MH079213-01A1/MH/NIMH NIH HHS/United States GR - AS1862/AS/Autism Speaks/United States PT - Journal Article PT - Research Support, N.I.H., Extramural PT - Research Support, Non-U.S. Gov't DEP - 20080201 PL - England TA - Cell Signal JT - Cellular signalling JID - 8904683 RN - 0 (Adaptor Proteins, Signal Transducing) RN - 0 (TSC2 protein, human) RN - 0 (Tsc2 protein, rat) RN - 0 (Tuberous Sclerosis Complex 2 Protein) RN - 0 (Tumor Suppressor Proteins) RN - EC 1.- (Mixed Function Oxygenases) RN - EC 2.3.2.23 (Ubiquitin-Conjugating Enzymes) RN - EC 2.3.2.27 (MYCBP2 protein, human) RN - EC 2.3.2.27 (Ubiquitin-Protein Ligases) RN - EC 2.7.- (Protein Kinases) RN - EC 2.7.1.1 (MTOR protein, human) RN - EC 2.7.1.1 (mTOR protein, rat) RN - EC 2.7.11.1 (TOR Serine-Threonine Kinases) SB - IM MH - Adaptor Proteins, Signal Transducing/chemistry/*metabolism MH - Amino Acid Sequence MH - Animals MH - Cells, Cultured MH - Humans MH - Mixed Function Oxygenases/chemistry/*metabolism MH - Molecular Sequence Data MH - Mutation, Missense MH - Neurons/metabolism MH - Phosphorylation MH - Protein Kinases/*metabolism MH - Protein Structure, Tertiary MH - Rats MH - Signal Transduction MH - TOR Serine-Threonine Kinases MH - Tuberous Sclerosis/genetics MH - Tuberous Sclerosis Complex 2 Protein MH - Tumor Suppressor Proteins/*metabolism MH - Ubiquitin-Conjugating Enzymes/metabolism MH - Ubiquitin-Protein Ligases/chemistry/*metabolism MH - Ubiquitination PMC - PMC2435383 MID - NIHMS50682 EDAT- 2008/03/01 09:00 MHDA- 2008/09/30 09:00 PMCR- 2009/06/01 CRDT- 2008/03/01 09:00 PHST- 2008/01/09 00:00 [received] PHST- 2008/01/21 00:00 [accepted] PHST- 2008/03/01 09:00 [pubmed] PHST- 2008/09/30 09:00 [medline] PHST- 2008/03/01 09:00 [entrez] PHST- 2009/06/01 00:00 [pmc-release] AID - S0898-6568(08)00035-1 [pii] AID - 10.1016/j.cellsig.2008.01.020 [doi] PST - ppublish SO - Cell Signal. 2008 Jun;20(6):1084-91. doi: 10.1016/j.cellsig.2008.01.020. Epub 2008 Feb 1.