Department of Cosmetic Health Science, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi, Gifu, 501-1196, Japan; TOA Inc., Nippon Life Yodoyabashi Bldg., 17F, 3-5-29, Kitahama, Chuo-ku, Osaka, 541-0041, Japan.
Department of Cosmetic Health Science, Gifu Pharmaceutical University, 1-25-4 Daigaku-nishi, Gifu, 501-1196, Japan.
Arch Biochem Biophys. 2024 Sep;759:110098. doi: 10.1016/j.abb.2024.110098. Epub 2024 Jul 14.
Mouse transmembrane protein 2 (mTMEM2) has been identified as a hyaluronidase, which has extracellularly G8 and GG domains and PbH1 repeats; however, our previously study showed that human TMEM2 (hTMEM2) is not a catalytic hyaluronidase due to the absence of the critical amino acid residues (His248/Ala303) in the GG domain. Naked mole-rats (NMRs) accumulate abundant high-molecular weight hyaluronan (HA) in their tissues, suggesting decreased HA degradation. Therefore, we aimed to evaluate the HA-degrading activity of NMR TMEM2 (nmrTMEM2) and compare it with those of mTMEM2 and hTMEM2. The amino acid residues of nmrTMEM2 (Asn247/Val302) are similar to Asn248/Phe303 of hTMEM2, and nmrTMEM2-expressing HEK293T cells showed negligible activity. We confirmed the significance of these amino acid residues using an inactive chimeric TMEM2 with the human GG domain, which acquired catalytic activity when Asn248/Phe303 was substituted with His248/Ala303. Semi-quantitative comparison of the activities of the membrane-fractions derived from m/h/nmrTMEM2-expressing HEK293T cells revealed that at least 20- and 14-fold higher amounts of nmr/hTMEM2 were required to degrade HA to the same extent as by mTMEM2. Thus, unlike mTMEM2, nmrTMEM2 is not a physiological hyaluronidase. The inability of nmrTMEM2 to degrade HA might partially account for the high-molecular-weight HA accumulation in NMR tissues.
鼠跨膜蛋白 2（mTMEM2）已被鉴定为一种透明质酸酶，其具有细胞外的 G8 和 GG 结构域和 PbH1 重复序列；然而，我们之前的研究表明，由于 GG 结构域中关键氨基酸残基（His248/Ala303）的缺失，人 TMEM2（hTMEM2）不是催化性透明质酸酶。裸鼹鼠（NMRs）在其组织中积累丰富的高分子量透明质酸（HA），表明 HA 降解减少。因此，我们旨在评估 NMR TMEM2（nmrTMEM2）的 HA 降解活性，并将其与 mTMEM2 和 hTMEM2 进行比较。nmrTMEM2（Asn247/Val302）的氨基酸残基与 hTMEM2 的 Asn248/Phe303 相似，表达 nmrTMEM2 的 HEK293T 细胞几乎没有活性。我们使用具有人 GG 结构域的无活性嵌合 TMEM2 证实了这些氨基酸残基的重要性，该嵌合 TMEM2 当 Asn248/Phe303 被 His248/Ala303 取代时获得了催化活性。从表达 m/h/nmrTMEM2 的 HEK293T 细胞的膜部分中进行的半定量比较表明，nmr/hTMEM2 的量至少需要 20 倍和 14 倍，才能将 HA 降解到与 mTMEM2 相同的程度。因此，与 mTMEM2 不同，nmrTMEM2 不是一种生理透明质酸酶。nmrTMEM2 不能降解 HA 可能部分解释了 NMR 组织中高分子量 HA 的积累。
