PTEN-induced putative kinase 1 (PINK1) is a mitochondrial serine/threonine-protein kinase encoded by the PINK1gene.[1][2]
It is thought to protect cells from stress-induced mitochondrial dysfunction. PINK1 activity causes the parkinprotein to bind to depolarized mitochondria to induce autophagy of those mitochondria.[3][4] PINK1 is processed by healthy mitochondria and released to trigger neuron differentiation.[5] Mutations in this gene cause one form of autosomal recessive early-onset Parkinson's disease.[6]
PINK1 is synthesized as a 63000 Da protein which is often cleaved by PARL, between the 103-Alanine and the 104-Phenylalanine residues, into a 53000 Da fragment.[7] PINK1 contains an N-terminal mitochondrial localization sequence, a putative transmembrane sequence, a Ser/Thr kinase domain, and a C-terminal regulatory sequence. The protein has been found to localize to the outer membrane of mitochondria, but can also be found throughout the cytosol. Experiments suggest the Ser/Thr kinase domain faces outward toward the cytosol, indicating a possible point of interaction with parkin.[8]
The structure of PINK1 has been solved and shows how the protein binds and phosphorylates its substrate ubiquitin.[9]
Function
PINK1 is intimately involved with mitochondrial quality control by identifying damaged mitochondria and targeting specific mitochondria for degradation. Healthy mitochondria maintain a membrane potential that can be used to import PINK1 into the inner membrane where it is cleaved by PARL and cleared from the outer membrane. Severely damaged mitochondria lack sufficient membrane potential to import PINK1, which then accumulates on the outer membrane. PINK1 then recruits parkin to target the damaged mitochondria for degradation through autophagy.[10] Due to the presence of PINK1 throughout the cytoplasm, it has been suggested that PINK1 functions as a "scout" to probe for damaged mitochondria.[11]
File:Degradation of damaged mitochondria with PINK1.pngA damaged mitochondria being recognized by PINK1. PINK1 builds up on the outer membrane of the mitochondria and recruits parkin. The PINK1/parkin pathway then designates the mitochondria for degradation by lysosomes.File:PINK1 with healthy mitochondria.pngA healthy mitochondria can import PINK1 where it is subsequently cleaved by PARL. This prevents any buildup of PINK1 and parkin is not recruited to the mitochondria.
PINK1 may also control mitochondria quality through mitochondrial fission. Through mitochondrial fission, a number of daughter mitochondria are created, often with an uneven distribution in membrane potential. Mitochondria with a strong, healthy membrane potential were more likely to undergo fusion than mitochondria with a low membrane potential. Interference with the mitochondrial fission pathway led to an increase in oxidized proteins and a decrease in respiration.[12] Without PINK1, parkin cannot efficiently localize to damaged mitochondria, while an over-expression of PINK1 causes parkin to localize to even healthy mitochondria.[13] Furthermore, mutations in both Drp1, a mitochondrial fission factor, and PINK1 were fatal in Drosophila models. However, an over-expression of Drp1 could rescue subjects deficient in PINK1 or parkin, suggesting mitochondrial fission initiated by Drp1 recreates the same effects of the PINK1/parkin pathway.[14]
In addition to mitochondrial fission, PINK1 has been implicated in mitochondrial motility. The accumulation of PINK1 and recruitment of parkin targets a mitochondria for degradation, and PINK1 may serve to enhance degradation rates by arresting mitochondrial motility. Over-expression of PINK1 produced similar effects to silencing Miro, a protein closely associated with mitochondrial migration.[15]
Another mechanism of mitochondrial quality control may arise through mitochondria-derived vesicles. Oxidative stress in mitochondria can produce potentially harmful compounds including improperly folded proteins or reactive oxygen species. PINK1 has been shown to facilitate the creation of mitochondria-derived vesicles which can separate reactive oxygen species and shuttle them toward lysosomes for degradation.[16]
Disease relevance
Parkinson's disease is often characterized by the degeneration of dopaminergenic neurons and associated with the build-up of improperly folded proteins and Lewy bodies. Mutations in the PINK1 protein have been shown to lead to a build-up of such improperly folded proteins in the mitochondria of both fly and human cells.[17] Specifically, mutations in the serine/threonine kinase domain have been found in a number of Parkinson's patients where PINK1 fails to protect against stress-induced mitochondrial dysfunction and apoptosis.[18]
References
↑Unoki M, Nakamura Y (Aug 2001). "Growth-suppressive effects of BPOZ and EGR2, two genes involved in the PTEN signaling pathway". Oncogene. 20 (33): 4457–65. doi:10.1038/sj.onc.1204608. PMID11494141.
↑Valente EM, Salvi S, Ialongo T, Marongiu R, Elia AE, Caputo V, Romito L, Albanese A, Dallapiccola B, Bentivoglio AR (Sep 2004). "PINK1 mutations are associated with sporadic early-onset parkinsonism". Ann Neurol. 56 (3): 336–41. doi:10.1002/ana.20256. PMID15349860.
Khan NL, Valente EM, Bentivoglio AR, Wood NW, Albanese A, Brooks DJ, Piccini P (2002). "Clinical and subclinical dopaminergic dysfunction in PARK6-linked parkinsonism: an 18F-dopa PET study". Ann. Neurol. 52 (6): 849–53. doi:10.1002/ana.10417. PMID12447943.
Bonifati V, Dekker MC, Vanacore N, Fabbrini G, Squitieri F, Marconi R, Antonini A, Brustenghi P, Dalla Libera A, De Mari M, Stocchi F, Montagna P, Gallai V, Rizzu P, van Swieten JC, Oostra B, van Duijn CM, Meco G, Heutink P (2003). "Autosomal recessive early onset parkinsonism is linked to three loci: PARK2, PARK6, and PARK7". Neurol. Sci. 23 Suppl 2: S59–60. doi:10.1007/s100720200069. PMID12548343.
Valente EM, Brancati F, Caputo V, Graham EA, Davis MB, Ferraris A, Breteler MM, Gasser T, Bonifati V, Bentivoglio AR, De Michele G, Dürr A, Cortelli P, Filla A, Meco G, Oostra BA, Brice A, Albanese A, Dallapiccola B, Wood NW (2003). "PARK6 is a common cause of familial parkinsonism". Neurol. Sci. 23 Suppl 2: S117–8. doi:10.1007/s100720200097. PMID12548371.
Nakajima A, Kataoka K, Hong M, Sakaguchi M, Huh NH (2004). "BRPK, a novel protein kinase showing increased expression in mouse cancer cell lines with higher metastatic potential". Cancer Lett. 201 (2): 195–201. doi:10.1016/S0304-3835(03)00443-9. PMID14607334.
Healy DG, Abou-Sleiman PM, Ahmadi KR, Muqit MM, Bhatia KP, Quinn NP, Lees AJ, Latchmann DS, Goldstein DB, Wood NW (2004). "The gene responsible for PARK6 Parkinson's disease, PINK1, does not influence common forms of parkinsonism". Ann. Neurol. 56 (3): 329–35. doi:10.1002/ana.20206. PMID15349859.
Hatano Y, Li Y, Sato K, Asakawa S, Yamamura Y, Tomiyama H, Yoshino H, Asahina M, Kobayashi S, Hassin-Baer S, Lu CS, Ng AR, Rosales RL, Shimizu N, Toda T, Mizuno Y, Hattori N (2004). "Novel PINK1 mutations in early-onset parkinsonism". Ann. Neurol. 56 (3): 424–7. doi:10.1002/ana.20251. PMID15349870.
Hatano Y, Sato K, Elibol B, Yoshino H, Yamamura Y, Bonifati V, Shinotoh H, Asahina M, Kobayashi S, Ng AR, Rosales RL, Hassin-Baer S, Shinar Y, Lu CS, Chang HC, Wu-Chou YH, Ataç FB, Kobayashi T, Toda T, Mizuno Y, Hattori N (2006). "PARK6-linked autosomal recessive early-onset parkinsonism in Asian populations". Neurology. 63 (8): 1482–5. doi:10.1001/archneur.63.10.1482. PMID15505170.
Healy DG, Abou-Sleiman PM, Gibson JM, Ross OA, Jain S, Gandhi S, Gosal D, Muqit MM, Wood NW, Lynch T (2006). "PINK1 (PARK6) associated Parkinson disease in Ireland". Neurology. 63 (8): 1486–8. doi:10.1212/01.wnl.0000142089.38301.8e. PMID15505171.
Rogaeva E, Johnson J, Lang AE, Gulick C, Gwinn-Hardy K, Kawarai T, Sato C, Morgan A, Werner J, Nussbaum R, Petit A, Okun MS, McInerney A, Mandel R, Groen JL, Fernandez HH, Postuma R, Foote KD, Salehi-Rad S, Liang Y, Reimsnider S, Tandon A, Hardy J, St George-Hyslop P, Singleton AB (2005). "Analysis of the PINK1 gene in a large cohort of cases with Parkinson disease". Arch. Neurol. 61 (12): 1898–904. doi:10.1001/archneur.61.12.1898. PMID15596610.
Deng H, Le WD, Zhang X, Pan TH, Jankovic J (2005). "G309D and W437OPA PINK1 mutations in Caucasian Parkinson's disease patients". Acta Neurol. Scand. 111 (6): 351–2. doi:10.1111/j.1600-0404.2005.00383.x. PMID15876334.
Li Y, Tomiyama H, Sato K, Hatano Y, Yoshino H, Atsumi M, Kitaguchi M, Sasaki S, Kawaguchi S, Miyajima H, Toda T, Mizuno Y, Hattori N (2005). "Clinicogenetic study of PINK1 mutations in autosomal recessive early-onset parkinsonism". Neurology. 64 (11): 1955–7. doi:10.1212/01.WNL.0000164009.36740.4E. PMID15955953.
