TMPRSS2

Intro TMPRSS2

Transmembrane protease serine 2 - Uniprot O15393

from uniprot: Facilitates human SARS coronavirus (SARS-CoV) infection via two independent mechanisms, proteolytic cleavage of ACE2, which might promote viral uptake, and cleavage of coronavirus spike glycoprotein which activates the glycoprotein for cathepsin L-independent host cell entry. Proteolytically cleaves and activates the spike glycoproteins of human coronavirus 229E (HCoV-229E) and human coronavirus EMC (HCoV-EMC) and the fusion glycoproteins F0 of Sendai virus (SeV), human metapneumovirus (HMPV), human parainfluenza 1, 2, 3, 4a and 4b viruses (HPIV). Essential for spread and pathogenesis of influenza A virus (strains H1N1, H3N2 and H7N9); involved in proteolytic cleavage and activation of hemagglutinin (HA) protein which is essential for viral infectivity.

(Meyer 2016 pmid: 23527573) also known as epitheliasin - first identified in 1997 - human chromosome 21 - protein of 492 amino acids [1], - anchored to the plasma membrane - belongs to the family of TTSPs (type II transmembrane serine proteases).

TTSPs are characterized by a short intracellular N-terminal domain, a transmembrane domain and a large extracellular domain containing a variable stem region and a C-terminal serine protease domain of the chymotrypsin S1 fold [2,3].

The TTSPs can be divided into four subfamilies on the basis of the phylogenetic analysis of the serine protease domain and the composition of the stem region [4], including the HAT (human airway-trypsinlike serine protease)/DESC, the matriptase, the hepsin/TMPRSS (transmembrane protease serine) and corin subfamilies.

TMPRSS2 belongs to the hepsin/TMPRSS subfamily, - contains six proteolytically active enzymes.

humans, TMPRSS2 is predominantly expressed in prostate, pancreatic and colon tissues, but also in lung, liver and kidney tissues [5,6].

the physiological role of the protein is still unknown [8]. TMPRSS2-knockout mice develop normally and survive to adulthood with no abnormalities in organ histology or function [8].

Two protein species of TMPRSS2 with apparent molecular masses of 70 and 32 kDa are described in literature. In cells and tissues, autocatalytic cleavage occurs between Arg255 and Ile256, providing the active protease [5]. The still membrane-bound protease can be partially shed and liberated into the extracellular space [9]. The protease domain contains a catalytic triad consisting of residues His296, Asp345 and Ser441 [1]

Substrates

(Meyer 2016 pmid: 23527573) amongst others ... cleave the precursor of the surface glycoprotein HA (haemagglutinin) of various influenza viruses at a monobasic cleavage site, including human viruses of subtypes H1, H2 and H3.

cleavage of the S protein by TMPRSS2 seems to facilitate the direct entry of the SARS-CoV from the cell surface independent of cathepsin L activity in the endosomal pathway [18]. In a recent study, it was described that the inhibition of TMPRSS2 by the non-specific serine protease inhibitor camostat caused a 10-fold reduction in infection of Calu3 cells by SARS-CoV [19].

PRMTSS2 structure

(Meyer 2016 pmid: 23527573) Although no crystal structure of TMPRSS2 is so far available, the catalytic domains of all trypsin-like serine proteases share a similar overall folding pattern.

Bacterial expression works but very inefficient

(Meyer 2016 pmid: 23527573) The expression of the catalytic domain of TMPRSS2 in E. coli according to a previous strategy for the preparation of matriptase [23] and its subsequent activation provided only a limited amount of active enzyme. Despite several attempts and modifications of the protocol, we could not identify a reliable refolding system, which provided larger quantities of active TMPRSS2 after the activation step with DAPase. In somecases, the protein also precipitated during the final activationwith DAPase. Therefore the preparation of active TMPRSS2requires further optimization to obtain sufficient amounts forstructure determination. Nevertheless, the activated crude enzymepreparation could be used for the first substrate and inhibitorscreening.