丨November
protein synthesis usually starts from methionine and is removed during the translation process. However, actin in cells does not follow this rule, because the synthesis of actin involves the removal of post-translational acetylated methionine. However, so far, removes protease that removes acetylated methionine. To this end, the Dutch Cancer Institute Thijn R. Brummelkamp Research group published a post in Science titled Actin maturation requires the ACTMAP/C19orf54 Protease, , was determined through proteomics analysis. The specific molecular biological mechanisms of C19orf54/ACTMAP actin maturation protease promotes actin maturation and regulates the cytoskeleton tissue structure, strength generation and cell migration.
There are 6 kinds of actin expression in the human body, two kinds of cytoplasmic actin, and four kinds of muscle actin 【1】. All actin requires N-terminal processing, which is called actin maturation 【2】. For beta and gamma-type actin molecules in the cytoplasm, the initial acetylated methionine was removed by unknown enzymes after translation by (Figure 1) . To study the actin maturation process, the authors generated an antibody that could recognize the N-terminus of beta actin immature. Since there is no mature beta actin antibody, the authors used mature gamma actin antibody as a replacement. Through haploid genetics, 【3-5】, the authors searched for the mutated gene in highly immature actin-stained cell populations through gene trap mutation. Among them, C19orf54 meets the target parameters and has the highest score. Compared with other targets, C19orf54 was never found in screens that were not associated with actin treatment, suggesting that the process is specific. Subsequently, according to the function of the factor, the authors renamed this to actin mature protease ACTMAP.
Figure 1 Looking for proteases that regulate actin maturation
The authors found that knocking out ACTMAP will lead to the maturation and accumulation of immature actin. Additionally, the authors found that knocking out ACTMAP did not affect the overall level of actin. Therefore, ACTMAP is crucial for actin maturation and stimulates the resection step of acetylated methionine in cytoplasmic actin. Since ACTMAP is an uncharacterized protein , the authors analyzed its predicted structure through the AlphaFold protein structure database, and it is speculated that it may have cysteine protease activity . To determine whether ACTMAP is really a cysteine protease, the authors used wild-type and cysteine mutant ACTMAP transgenes to supplement ACTMAP knockout cells. Wild-type ACTMAP completely restores the process of actin, which is prevented by point mutations in cysteine . Therefore, ACTMAP cysteine protease activity is crucial for actin maturation. This was also demonstrated by subsequent in vitro recombinant protease activity tests.
Further, the authors analyzed the protein interaction group of ACTMAP and found that actin and actin-related proteins are highly enriched, indicating that ACTMAP specifically targets actin. Among them, the actin binding proteins PFN1 and PFN2A/B interact with ACTMAP to promote efficient actin maturation and processing.
In order to identify the physiological level of ACTMAP functions, the authors knocked out Actmap found that Knockout does not cause death in mice, but will cause multiple actin maturation defects. Measurement of the stretching parameters of soleus muscles in vitro separation showed that Actmap knockdown will lead to changes in muscle strength, muscle fiber length and stretching ability.
Overall, the authors' work identified the actin mature protease ACTMAP, which provided an answer to unknown gaps in the actin maturation process, and confirmed that the protein has cysteine protease activity and is very critical to the functions of mouse muscle strength and other functions.
Original link:
http://doi.org/10.1126/science.abq5082
Platformer: 11
References
1. T. D. Pollard, J. A. Cooper, Science 326, 1208–1212 (2009).
2. S. Varland, J. Vandekerckhove, A. Drazic, Trends Biochem. Sci. 44, 502–516 (2019)
3. M. Brockmann et al., Nature 546, 307–311 (2017).
4. M. E. W. Logtenberg et al., Nat. Med. 25, 612–619 (2019).
5. J. Nieuwenhuis et al., Science 358, 1453–1456 (2017).
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