Abstract
ABSTRACTThe human zinc metalloprotease ZMPSTE24 is an integral membrane protein crucial for the final step in the biogenesis of the nuclear scaffold protein lamin A, encoded by LMNA. After farnesylation and carboxyl methylation of its C-terminal CAAX motif, the lamin A precursor (prelamin A) undergoes proteolytic removal of its modified C-terminal 15 amino acids by ZMPSTE24. Mutations in LMNA or ZMPSTE24 that impede this prelamin A cleavage step cause the premature aging disease Hutchinson-Gilford progeria syndrome (HGPS), and the related progeroid disorders mandibuloacral dysplasia type B (MAD-B) and restrictive dermopathy (RD). Here, we report the development of a ‘humanized yeast system’ to assay ZMPSTE24-dependent cleavage of prelamin A and examine the eight known disease-associated ZMPSTE24 missense mutations. All mutations show diminished prelamin A processing and fall into three classes, with defects in activity, protein stability or both. Notably, some ZMPSTE24 mutants can be rescued by deleting the E3 ubiquitin ligase Doa10, involved in endoplasmic reticulum (ER)-associated degradation of misfolded membrane proteins, or by treatment with the proteasome inhibitor bortezomib. This finding may have important therapeutic implications for some patients. We also show that ZMPSTE24-mediated prelamin A cleavage can be uncoupled from the recently discovered role of ZMPSTE24 in clearance of ER membrane translocon-clogged substrates. Together with the crystal structure of ZMPSTE24, this humanized yeast system can guide structure-function studies to uncover mechanisms of prelamin A cleavage, translocon unclogging, and membrane protein folding and stability.
Highlights
The integral membrane zinc metalloprotease ZMPSTE24 has a crucial role in human health and longevity through its role in the maturation of the nuclear scaffold protein lamin A from its precursor, prelamin A (Bergo et al, 2002; Michaelis and Hrycyna, 2013; Pendas et al, 2002)
We show that the eight currently known disease-causing ZMPSTE24 missense alleles (Table 1) all have decreased prelamin A cleavage in vivo and fall into distinct classes: those that only affect cleavage activity, those that affect in vivo protein stability through endoplasmic reticulum (ER)-associated degradation (ERAD) by the ubiquitinproteasome system (UPS), and those that affect both
ZMPSTE24 can perform the upstream cleavage of its bona fide substrate prelamin A in yeast We previously showed that human ZMPSTE24 could functionally replace its yeast homolog Ste24 for the proteolytic maturation of its non-native substrate, the yeast mating pheromone a-factor (Barrowman and Michaelis, 2009; Schmidt et al, 2000; Tam et al, 1998)
Summary
The integral membrane zinc metalloprotease ZMPSTE24 has a crucial role in human health and longevity through its role in the maturation of the nuclear scaffold protein lamin A from its precursor, prelamin A (Bergo et al, 2002; Michaelis and Hrycyna, 2013; Pendas et al, 2002). Defects in prelamin A processing by ZMPSTE24 are a primary cause of progeria (Capell and Collins, 2006; Davies et al, 2009; Gordon et al, 2014; Michaelis and Hrycyna, 2013). The premature aging disorder Hutchinson-Gilford progeria syndrome (HGPS; OMIM #176670) results from mutations in the LMNA gene (encoding prelamin A) that block ZMPSTE24 processing, whereas the related progeroid diseases mandibuloacral dysplasia type B (MAD-B; OMIM #608612) and restrictive dermopathy (RD; OMIM #275210) result from mutations in ZMPSTE24 that diminish protease function (Barrowman et al, 2012b; Davies et al, 2009; De Sandre-Giovannoli et al, 2003; Eriksson et al, 2003; Navarro et al, 2014). Understanding the mechanistic details of prelamin A processing by ZMPSTE24 is crucial for designing therapeutic approaches for these progeroid diseases and might provide insights into the normal physiological aging process
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
