NaStEP, an essential protein for self-incompatibility in Nicotiana, performs a dual activity as a proteinase inhibitor and as a voltage-dependent channel blocker
Por:
Cruz-Zamora Y., Nájera-Torres E., Noriega-Navarro R., Torres-Rodríguez M.D., Bernal-Gracida L.A., García-Valdés J., Juárez-Díaz J.A., Cruz-García F.
Publicada:
1 ene 2020
Resumen:
The S-specific pollen rejection response in Nicotiana depends on the interaction between S-RNase and a suite of SLF proteins. However, the biochemical pathway requires other essential proteins. One of them is the stigmatic protein NaStEP, which belongs to the Kunitz-type protease inhibitor family. Within the pollen tubes, NaStEP is a positive regulator of HT-B stability, likely inhibiting its degradation and, additionally, interacts with NaSIPP, a mitochondrial phosphate carrier. To gain a deeper understanding of the biochemical role of NaStEP in pollen rejection, we evaluated whether the activity of NaStEP as protease inhibitor is specific to a particular type of protease and whether it has the function of a voltage-dependent channel (VDC) blocker. Our findings indicate that, in vitro, NaStEP inhibits a subtilisin-like protease in an irreversible manner, but not other proteases, such as thermolysin and papain. Furthermore, we found that subtilisin processes the native NaStEP (24 kDa) into two lower molecular weight peptides of 21 and 14 kDa. Moreover, when we incubated NaStEP along with Xenopus leavis oocytes expressing the voltage-dependent potassium channel Kv 1.3, the current was blocked, indicating that NaStEP acts as a VDC blocker. These data allow us to propose NaStEP acts as a key molecule with two functions, one protecting HT-B from degradation by inhibiting a subtilisin-like protease and the second one by forming a complex with a mitochondrial VDC that could destabilize the mitochondria to trigger cell death, which would reinforce S-specific pollen rejection in Nicotiana. © 2020 Elsevier Masson SAS
Filiaciones:
Cruz-Zamora Y.:
Departamento de Bioquímica, Facultad de Química, Universidad Nacional Autónoma de México, Cd. Mx, 04510, Mexico
Univ Nacl Autonoma Mexico, Fac Quim, Dept Bioquim, Cd Mx 04510, Mexico
Nájera-Torres E.:
Departamento de Bioquímica, Facultad de Química, Universidad Nacional Autónoma de México, Cd. Mx, 04510, Mexico
Univ Nacl Autonoma Mexico, Fac Quim, Dept Bioquim, Cd Mx 04510, Mexico
Noriega-Navarro R.:
Departamento de Química Analítica, Facultad de Química, Universidad Nacional Autónoma de México, Cd. Mx, 04510, Mexico
Univ Nacl Autonoma Mexico, Fac Quim, Dept Quim Analit, Cd Mx 04510, Mexico
Torres-Rodríguez M.D.:
Departamento de Bioquímica, Facultad de Química, Universidad Nacional Autónoma de México, Cd. Mx, 04510, Mexico
Univ Nacl Autonoma Mexico, Fac Quim, Dept Bioquim, Cd Mx 04510, Mexico
Bernal-Gracida L.A.:
Departamento de Bioquímica, Facultad de Química, Universidad Nacional Autónoma de México, Cd. Mx, 04510, Mexico
Univ Nacl Autonoma Mexico, Fac Quim, Dept Bioquim, Cd Mx 04510, Mexico
García-Valdés J.:
Departamento de Química Analítica, Facultad de Química, Universidad Nacional Autónoma de México, Cd. Mx, 04510, Mexico
Univ Nacl Autonoma Mexico, Fac Quim, Dept Quim Analit, Cd Mx 04510, Mexico
Juárez-Díaz J.A.:
Departamento de Biología Comparada, Facultad de Ciencias, Universidad Nacional Autónoma de México, Cd. Mx, 04510, Mexico
Univ Nacl Autonoma Mexico, Fac Ciencias, Dept Biol Comparada, Cd Mx 04510, Mexico
Cruz-García F.:
Departamento de Bioquímica, Facultad de Química, Universidad Nacional Autónoma de México, Cd. Mx, 04510, Mexico
Univ Nacl Autonoma Mexico, Fac Quim, Dept Bioquim, Cd Mx 04510, Mexico
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