26S proteasome non-ATPase regulatory subunit 14, also known as 26S proteasome non-ATPase subunit Rpn11, is an enzyme that in humans is encoded by the PSMD14gene.[1][2] This protein is one of the 19 essential subunits of a complete assembled 19S proteasome complex.[3] Nine subunits Rpn3, Rpn5, Rpn6, Rpn7, Rpn8, Rpn9, Rpn11, SEM1(Yeast analogue for human protein DSS1), and Rpn12 form the lid sub complex of 19S regulatory particle for proteasome complex.[3]
The gene PSMD14 encodes one of 26S proteasome non-ATPase subunit.[2] The human gene PSMD14 has 12 Exons and locates at chromosome band 2q24.2.
Protein
The human protein 26S proteasome non-ATPase regulatory subunit 14 is 34.6 kDa in size and composed of 310 amino acids. The calculated theoretical pI of this protein is 6.06.[4]
Complex assembly
26S proteasome complex is usually consisted of a 20S core particle (CP, or 20S proteasome) and one or two 19S regulatory particles (RP, or 19S proteasome) on either one side or both side of the barrel-shaped 20S. The CP and RPs pertain distinct structural characteristics and biological functions. In brief, 20S sub complex presents three types proteolytic activities, including caspase-like, trypsin-like, and chymotrypsin-like activities. These proteolytic active sites located in the inner side of a chamber formed by 4 stacked rings of 20S subunits, preventing random protein-enzyme encounter and uncontrolled protein degradation. The 19S regulatory particles can recognize ubiquitin-labeled protein as degradation substrate, unfold the protein to linear, open the gate of 20S core particle, and guide the substate into the proteolytic chamber. To meet such functional complexity, 19S regulatory particle contains at least 18 constitutive subunits. These subunits can be categorized into two classes based on the ATP dependence of subunits, ATP-dependent subunits and ATP-independent subunits. According to the protein interaction and topological characteristics of this multisubunit complex, the 19S regulatory particle is composed of a base and a lid subcomplex. The base consists of a ring of six AAA ATPases (Subunit Rpt1-6, systematic nomenclature) and four non-ATPase subunits (Rpn1, Rpn2, Rpn10, and Rpn13).s The lid sub complex of 19S regulatory particle consisted of 9 subunits. The assembly of 19S lid is independent to the assembly process of 19S base. Two assembly modules, Rpn5-Rpn6-Rpn8-Rpn9-Rpn11 modules and Rpn3-Rpn7-SEM1 modules were identified during 19S lid assembly using yeast proteasome as a model complex.[5][6][7][8] The subunit Rpn12 incorporated into 19S regulatory particle when 19S lid and base bind together.[9] Among these lid subunits, protein Rpn11 presents the metalloproteases activity to hydrolyze the ubiquitin molecules from the poly-ubiquitin chain before protein substrates are unfolded and degraded.[10][11] During substrate degradation, the 19S regulatory particles undergo a conformation switch that is characterized by a rearranged ATPase ring with uniform subunit interfaces. Notably, Rpn11 migrates from an occluded position to directly above the central pore, thus facilitating substrate deubiquitination concomitant with translocation.[12]
Function
As the degradation machinery that is responsible for ~70% of intracellular proteolysis,[13] proteasome complex (26S proteasome) plays a critical roles in maintaining the homeostasis of cellular proteome. Accordingly, misfolded proteins and damaged protein need to be continuously removed to recycle amino acids for new synthesis; in parallel, some key regulatory proteins fulfill their biological functions via selective degradation; furthermore, proteins are digested into peptides for MHC class I antigen presentation. To meet such complicated demands in biological process via spatial and temporal proteolysis, protein substrates have to be recognized, recruited, and eventually hydrolyzed in a well controlled fashion. Thus, 19S regulatory particle pertains a series of important capabilities to address these functional challenges. To recognize protein as designated substrate, 19S complex has subunits that are capable to recognize proteins with a special degradative tag, the ubiquitinylation. It also have subunits that can bind with nucleotides (e.g., ATPs) in order to facilitate the association between 19S and 20S particles, as well as to cause confirmation changes of alpha subunit C-terminals that form the substate entrance of 20S complex.
Protein Rpn11 presents the metalloproteases activity to hydrolyze the ubiquitin molecules from the poly-ubiquitin chain before protein substrates are unfolded and degraded[10]
Clinical significance
The Proteasome and its subunits are of clinical significance for at least two reasons: (1) a compromised complex assembly or a dysfunctional proteasome can be associated with the underlying pathophysiology of specific diseases, and (2) they can be exploited as drug targets for therapeutic interventions. More recently, more effort has been made to consider the proteasome for the development of novel diagnostic markers and strategies. An improved and comprehensive understanding of the pathophysiology of the proteasome should lead to clinical applications in the future.
The proteasomes form a pivotal component for the Ubiquitin-Proteasome System (UPS)[14] and corresponding cellular Protein Quality Control (PQC). Protein ubiquitination and subsequent proteolysis and degradation by the proteasome are important mechanisms in the regulation of the cell cycle, cell growth and differentiation, gene transcription, signal transduction and apoptosis.[15] Subsequently, a compromised proteasome complex assembly and function lead to reduced proteolytic activities and the accumulation of damaged or misfolded protein species. Such protein accumulation may contribute to the pathogenesis and phenotypic characteristics in neurodegenerative diseases,[16][17] cardiovascular diseases,[18][19][20] inflammatory responses and autoimmune diseases,[21] and systemic DNA damage responses leading to malignancies.[22]
↑Spataro V, Toda T, Craig R, Seeger M, Dubiel W, Harris AL, Norbury C (Nov 1997). "Resistance to diverse drugs and ultraviolet light conferred by overexpression of a novel human 26 S proteasome subunit". The Journal of Biological Chemistry. 272 (48): 30470–5. doi:10.1074/jbc.272.48.30470. PMID9374539.
↑Le Tallec B, Barrault MB, Guérois R, Carré T, Peyroche A (Feb 2009). "Hsm3/S5b participates in the assembly pathway of the 19S regulatory particle of the proteasome". Molecular Cell. 33 (3): 389–99. doi:10.1016/j.molcel.2009.01.010. PMID19217412.
↑Fukunaga K, Kudo T, Toh-e A, Tanaka K, Saeki Y (Jun 2010). "Dissection of the assembly pathway of the proteasome lid in Saccharomyces cerevisiae". Biochemical and Biophysical Research Communications. 396 (4): 1048–53. doi:10.1016/j.bbrc.2010.05.061. PMID20471955.
↑Rock KL, Gramm C, Rothstein L, Clark K, Stein R, Dick L, Hwang D, Goldberg AL (Sep 1994). "Inhibitors of the proteasome block the degradation of most cell proteins and the generation of peptides presented on MHC class I molecules". Cell. 78 (5): 761–71. doi:10.1016/s0092-8674(94)90462-6. PMID8087844.
↑Goldberg AL, Stein R, Adams J (Aug 1995). "New insights into proteasome function: from archaebacteria to drug development". Chemistry & Biology. 2 (8): 503–8. doi:10.1016/1074-5521(95)90182-5. PMID9383453.
↑Sulistio YA, Heese K (Jan 2015). "The Ubiquitin-Proteasome System and Molecular Chaperone Deregulation in Alzheimer's Disease". Molecular Neurobiology. 53: 905–31. doi:10.1007/s12035-014-9063-4. PMID25561438.
↑ 21.021.1Karin M, Delhase M (Feb 2000). "The I kappa B kinase (IKK) and NF-kappa B: key elements of proinflammatory signalling". Seminars in Immunology. 12 (1): 85–98. doi:10.1006/smim.2000.0210. PMID10723801.
↑Checler F, da Costa CA, Ancolio K, Chevallier N, Lopez-Perez E, Marambaud P (Jul 2000). "Role of the proteasome in Alzheimer's disease". Biochimica et Biophysica Acta. 1502 (1): 133–8. doi:10.1016/s0925-4439(00)00039-9. PMID10899438.
↑ 24.024.1Chung KK, Dawson VL, Dawson TM (Nov 2001). "The role of the ubiquitin-proteasomal pathway in Parkinson's disease and other neurodegenerative disorders". Trends in Neurosciences. 24 (11 Suppl): S7–14. doi:10.1016/s0166-2236(00)01998-6. PMID11881748.
↑ 25.025.1Ikeda K, Akiyama H, Arai T, Ueno H, Tsuchiya K, Kosaka K (Jul 2002). "Morphometrical reappraisal of motor neuron system of Pick's disease and amyotrophic lateral sclerosis with dementia". Acta Neuropathologica. 104 (1): 21–8. doi:10.1007/s00401-001-0513-5. PMID12070660.
↑Manaka H, Kato T, Kurita K, Katagiri T, Shikama Y, Kujirai K, Kawanami T, Suzuki Y, Nihei K, Sasaki H (May 1992). "Marked increase in cerebrospinal fluid ubiquitin in Creutzfeldt–Jakob disease". Neuroscience Letters. 139 (1): 47–9. doi:10.1016/0304-3940(92)90854-z. PMID1328965.
↑Mathews KD, Moore SA (Jan 2003). "Limb-girdle muscular dystrophy". Current Neurology and Neuroscience Reports. 3 (1): 78–85. doi:10.1007/s11910-003-0042-9. PMID12507416.
↑Mayer RJ (Mar 2003). "From neurodegeneration to neurohomeostasis: the role of ubiquitin". Drug News & Perspectives. 16 (2): 103–8. doi:10.1358/dnp.2003.16.2.829327. PMID12792671.
↑Powell SR (Jul 2006). "The ubiquitin-proteasome system in cardiac physiology and pathology". American Journal of Physiology. Heart and Circulatory Physiology. 291 (1): H1–H19. doi:10.1152/ajpheart.00062.2006. PMID16501026.
↑Ben-Neriah Y (Jan 2002). "Regulatory functions of ubiquitination in the immune system". Nature Immunology. 3 (1): 20–6. doi:10.1038/ni0102-20. PMID11753406.
↑Egerer K, Kuckelkorn U, Rudolph PE, Rückert JC, Dörner T, Burmester GR, Kloetzel PM, Feist E (Oct 2002). "Circulating proteasomes are markers of cell damage and immunologic activity in autoimmune diseases". The Journal of Rheumatology. 29 (10): 2045–52. PMID12375310.
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Nabhan JF, Ribeiro P (Jun 2006). "The 19 S proteasomal subunit POH1 contributes to the regulation of c-Jun ubiquitination, stability, and subcellular localization". The Journal of Biological Chemistry. 281 (23): 16099–107. doi:10.1074/jbc.M512086200. PMID16569633.
Gallery M, Blank JL, Lin Y, Gutierrez JA, Pulido JC, Rappoli D, Badola S, Rolfe M, Macbeth KJ (Jan 2007). "The JAMM motif of human deubiquitinase Poh1 is essential for cell viability". Molecular Cancer Therapeutics. 6 (1): 262–8. doi:10.1158/1535-7163.MCT-06-0542. PMID17237285.
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