6itu | pdb_00006itu
Crystal Structure of the GULP1 PTB domain-APP peptide complex
Structural highlights
Function[GULP1_HUMAN] May function as an adapter protein. Required for efficient phagocytosis of apoptotic cells. Modulates cellular glycosphingolipid and cholesterol transport. May play a role in the internalization and endosomal trafficking of various LRP1 ligands, such as PSAP. Increases cellular levels of GTP-bound ARF6.[1] [2] [3] [4] Publication Abstract from PubMedAmyloid-beta (Abeta) is derived from the proteolytic processing of amyloid precursor protein (APP), and the deposition of extracellular Abeta to form amyloid plaques is a pathologic hallmark of Alzheimer's disease (AD). Although reducing Abeta generation and accumulation has been proposed as a means of treating the disease, adverse side effects and unsatisfactory efficacy have been reported in several clinical trials that sought to lower Abeta levels. Engulfment adaptor phosphotyrosine-binding (PTB) domain containing 1 (GULP1) is a molecular adaptor that has been shown to interact with APP to alter Abeta production. Therefore, the modulation of the GULP1-APP interaction may be an alternative approach to reducing Abeta. However, the mechanisms that regulate GULP1-APP binding remain elusive. As GULP1 is a phosphoprotein, and because phosphorylation is a common mechanism that regulates protein interaction, we anticipated that GULP1 phosphorylation would influence GULP1-APP interaction and thereby Abeta production. We show here that the phosphorylation of GULP1 threonine 35 (T35) reduces GULP1-APP interaction and suppresses the stimulatory effect of GULP1 on APP processing. The residue is phosphorylated by an isoform of atypical PKC (PKCzeta). Overexpression of PKCzeta reduces both GULP1-APP interaction and GULP1-mediated Abeta generation. Moreover, the activation of PKCzeta via insulin suppresses APP processing. In contrast, GULP1-mediated APP processing is enhanced in PKCzeta knockout cells. Similarly, PKC iota, another member of atypical PKC, also decreases GULP1-mediated APP processing. Intriguingly, our X-ray crystal structure of GULP1 PTB-APP intracellular domain (AICD) peptide reveals that GULP1 T35 is not located at the GULP1-AICD binding interface; rather, it immediately precedes the beta1-alpha2 loop that forms a portion of the binding groove for the APP helix alphaC. Phosphorylating the residue may induce an allosteric effect on the conformation of the binding groove. Our results indicate that GULP1 T35 phosphorylation is a mechanism for the regulation of GULP1-APP interaction and thereby APP processing. Moreover, the activation of atypical PKC, such as by insulin, may confer a beneficial effect on AD by lowering GULP1-mediated Abeta production.-Chau, D. D.-L., Yung, K. W.-Y., Chan, W. W.-L., An, Y., Hao, Y., Chan, H.-Y. E., Ngo, J. C.-K., Lau, K.-F. Attenuation of amyloid-beta generation by atypical protein kinase C-mediated phosphorylation of engulfment adaptor PTB domain containing 1 threonine 35. Attenuation of amyloid-beta generation by atypical protein kinase C-mediated phosphorylation of engulfment adaptor PTB domain containing 1 threonine 35.,Chau DD, Yung KW, Chan WW, An Y, Hao Y, Chan HE, Ngo JC, Lau KF FASEB J. 2019 Aug 5:fj201802825RR. doi: 10.1096/fj.201802825RR. PMID:31373844[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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