Gohlke Sabrina, Mishto Michele, Textoris-Taube Kathrin, Keller Christin, Giannini Carolin, Vasuri Francesco, Capizzi Elisa, D'Errico-Grigioni Antonia, Kloetzel Peter-Michael, Dahlmann Burkhardt
Institute of Biochemistry, Charité-Universitätsmedizin Berlin, CCM, CharitéCrossOver, Charitéplatz 1, 10117, Berlin, Germany.
Age (Dordr). 2014 Feb;36(1):57-72. doi: 10.1007/s11357-013-9543-x. Epub 2013 May 22.
Aging induces alterations of tissue protein homoeostasis. To investigate one of the major systems catalysing intracellular protein degradation we have purified 20S proteasomes from rat liver of young (2 months) and aged (23 months) animals and separated them into three subpopulations containing different types of intermediate proteasomes with standard- and immuno-subunits. The smallest subpopulation ΙΙΙ and the major subpopulation Ι comprised proteasomes containing immuno-subunits β1i and β5i beside small amounts of standard-subunits, whereas proteasomes of subpopulation ΙΙ contained only β5i beside standard-subunits. In favour of a relative increase of the major subpopulation Ι, subpopulation ΙΙ and ΙΙΙ were reduced for about 55 % and 80 %, respectively, in aged rats. Furthermore, in all three 20S proteasome subpopulations from aged animals standard-active site subunits were replaced by immuno-subunits. Overall, this transformation resulted in a relative increase of immuno-subunit-containing proteasomes, paralleled by reduced activity towards short fluorogenic peptide substrates. However, depending on the substrate their hydrolysing activity of long polypeptide substrates was significantly higher or unchanged. Furthermore, our data revealed an altered MHC class I antigen-processing efficiency of 20S proteasomes from liver of aged rats. We therefore suggest that the age-related intramolecular alteration of hepatic proteasomes modifies its cleavage preferences without a general decrease of its activity. Such modifications could have implications on protein homeostasis as well as on MHC class I antigen presentation as part of the immunosenescence process.
衰老会引发组织蛋白质稳态的改变。为了研究催化细胞内蛋白质降解的主要系统之一，我们从年轻（2个月）和老龄（23个月）大鼠的肝脏中纯化了20S蛋白酶体，并将它们分离成三个亚群，这些亚群包含不同类型的具有标准亚基和免疫亚基的中间蛋白酶体。最小的亚群III和主要亚群I包含除少量标准亚基外还含有免疫亚基β1i和β5i的蛋白酶体，而亚群II的蛋白酶体除标准亚基外仅含有β5i。老龄大鼠中，主要亚群I相对增加，亚群II和III分别减少了约55%和80%。此外，在老龄动物的所有三个20S蛋白酶体亚群中，标准活性位点亚基被免疫亚基取代。总体而言，这种转变导致含免疫亚基的蛋白酶体相对增加，同时对短荧光肽底物的活性降低。然而，根据底物的不同，它们对长多肽底物的水解活性显著更高或不变。此外，我们的数据显示老龄大鼠肝脏中20S蛋白酶体的MHC I类抗原加工效率发生了改变。因此，我们认为肝脏蛋白酶体与年龄相关的分子内改变改变了其切割偏好，但并未使其活性普遍降低。这种修饰可能对蛋白质稳态以及作为免疫衰老过程一部分的MHC I类抗原呈递产生影响。
