A new paradigm for Prelamin A proteolytic processing by ZMPSTE24: the upstream SY^LL cleavage occurs first and there is no CaaX processing by ZMPSTE24

Nie, L.; Spear, E.; Babatz, T. D.; Quigley, A.; Dong, Y. Y.; Chu, A.; Rotty, B.; Chalk, R.; Mukhopadhyay, S. M. M.; Burgess-Brown, N. A.; Pike, A. C. W.; Young, S. G.; Michaelis, S.; Carpenter, E. P.

doi:10.1101/2020.05.13.093849

bioRxiv · 10.1101/2020.05.13.093849

A new paradigm for Prelamin A proteolytic processing by ZMPSTE24: the upstream SY^LL cleavage occurs first and there is no CaaX processing by ZMPSTE24

Nie, L.·Spear, E.·Babatz, T. D.·Quigley, A.·Dong, Y. Y.·Chu, A.·Rotty, B.·Chalk, R.·Mukhopadhyay, S. M. M.·Burgess-Brown, N. A.·Pike, A. C. W.·Young, S. G.·Michaelis, S.·Carpenter, E. P.

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Abstract

Human ZMPSTE24, an integral membrane zinc metalloprotease, is required for conversion of prelamin A to mature lamin A, a component of the nuclear lamina and failure of this processing causes premature ageing disorders. ZMPSTE24 has also been implicated in both type 2 diabetes mellitus and in viral-host response mechanisms, but to date its only confirmed substrate is the precursor for lamin A. Prelamin A is thought to undergo four C-terminal post-translational modifications in the following order: farnesylation, SIM tripeptide cleavage, carboxymethylation and upstream "SY^LL" cleavage. Here we present evidence that the sequence of events does not follow the accepted dogma. We assessed cleavage of long human prelamin A sequence peptides by purified human ZMPSTE24 combined with FRET and mass spectrometry to detect products. Surprisingly, we found that the "SY^LL" cleavage occurs before and independent of the C-terminal CSIM modifications. We also found that ZMPSTE24 does not perform the predicted C^SIM tripeptide cleavage, but rather it removes an IM dipeptide. ZMPSTE24 can perform a tripeptide cleavage with a canonical CaaX box (C: cysteine; a: aliphatic; X: any residue), but the C-terminus of prelamin A is not a true CaaX sequence. Regardless of the C-terminal modifications of prelamin A, ZMPSTE24 can perform upstream SY^LL cleavage, thus removing the unwanted farnesylated C-terminus. Therefore, it is failure of SY^LL cleavage, not the C-terminal processing that is the likely cause of progeroid disorders.

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Nie, L., Spear, E., Babatz, T. D., Quigley, A., Dong, Y. Y., Chu, A., Rotty, B., Chalk, R., Mukhopadhyay, S. M. M., Burgess-Brown, N. A., Pike, A. C. W., Young, S. G., Michaelis, S., Carpenter, E. P.. 2020-05-13. A new paradigm for Prelamin A proteolytic processing by ZMPSTE24: the upstream SY^LL cleavage occurs first and there is no CaaX processing by ZMPSTE24. https://doi.org/10.1101/2020.05.13.093849

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