Role of Virus Attack
Angiotensin converting enzyme 2 (ACE2), a metallo-
peptidase, has been confirmed to effectively bind to the
S1 domain of the spike protein on SARS-CoV. Therefore,
ACE2 is considered to be a functional receptor of SARS-
CoV [11]. Researchers described the full-length genome
sequence of SARS-CoV-2 from 5 patients and found that
79.5% of SARS-CoV-2 sequences are homologous to
SARS -CoV [12]. Moreover, they share the same func-
tional receptor, i.e., ACE2, and have an affinity compa-
rable that of human ACE2 (hACE2) [12, 13]. Recently the
specific structure of ACE2 was discovered by cryoelec-
tronic microscopy and the multiple conformational states
of the SARS-CoV-2 S glycoprotein were demonstrated at
a 3.0-Å resolution [13, 14]. hACE2 is not only expressed
in lung tissue but it can also be detected in the kidneys,
mainly in proximal tubules, afferent arterioles, collecting
ducts, and the thick ascending limb of Helen [15]. In ad-
dition, viral nucleic acid could also be found in urine in 4
out of 58 (6.9%), suggesting that the kidneys might be the
target of this novel coronavirus [16]. Recently, Diao et al.
[10] demonstrated that SARS-CoV-2 mainly induced
acute tubular necrosis by infecting kidney tubules direct-
ly. Immunohistochemistry demonstrated that the NP an-
tigen of SARS-CoV-2 was accumulated in the cytoplasm
of kidney tubules instead of glomeruli based on the au-
topsy findings of 6 COVID-19 subjects with renal func-
tion impairment prior to death [10]. Besides, Su et al. [17]
found the virus particles in the cytoplasm of renal proxi-
mal tubular epithelium and podocytes but less so in distal
tubules. SARS-CoV nucleoprotein was analyzed in 6 cas-
es, and 3 showed positive granular staining in a nuclear
or cytoplasm pattern in tubular epithelium. These results
provide direct evidence that the SARS-CoV-2 virus can
directly infect the renal tubular epithelium and podo-
cytes, which may induce AKI in COVID-19 patients [17].
Thus, the novel coronavirus can induce kidney injury di-
rectly via hACE2 or other receptors like SARS-CoV, but
the exact mechanism still needs to be clarified.
