research groups
Cell Signal Transduction Networks
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Our work aims at the multifactorial study of cellular physiological parameters that aid in the interpretation and understanding of intracellular signaling pathways from a systems biology perspective.
To achieve this goal, we employ various tools that enable the simultaneous interpretation of multiple intracellular factors. Our group uses mouse sperm as our primary cellular model. Since sperm are transcriptionally and translationally inactive, they represent an exceptional model for the study of intracellular signaling mechanisms based on post-translational modifications.
Furthermore, studies derived from basic research on mouse sperm enable extrapolation to human sperm, which has implications for clinical reproduction, and to commercial species such as horses and cattle.
In mammals, sperm are not fertilizable at the time of ejaculation. They acquire this capacity within the female reproductive tract in a process called capacitation. Capacitation in mice can be achieved in the laboratory by incubating sperm for as little as one hour in defined culture media.
Current knowledge indicates that the functional changes leading to capacitation not only do not respond to a linear cascade of events, but rather a combination of both simultaneous and sequential processes. Some of these processes occur as soon as sperm are released from the epididymis, while other changes occur more slowly, being triggered only after a certain period under conditions that promote the sperm’s fertilizing capacity.
At the biological level, sperm capacitation is associated with both a change in flagellar beating called hyperactivation and the sperm’s ability to trigger the process called acrosomal exocytosis in response to a physiological agonist.
Protein kinase PKA (PKA) plays a fundamental role in both the fast and slow events associated with capacitation.
These events include: 1) hyperpolarization of the sperm plasma membrane; 2) increased cytoplasmic Ca2+ concentration; 3) activation of Tyr kinases; 4) both inactivation and activation of different Thr/Ser phosphatases; 5) modification of the lipid constitution of the plasma membrane; 6) actin polymerization.
With these events in mind, it emerges that the sperm is presented as an excellent model for the study of signaling cascades, considering the processes that are triggered within an hour, added to the ease of obtaining samples.
Our laboratory is currently focused on understanding the mechanisms by which PKA activity is regulated during capacitation, triggering plasma membrane hyperpolarization. This hyperpolarization, as in other cell types, is key to enabling subsequent processes, such as acrosomal exocytosis in sperm. The mechanisms by which PKA promotes hyperpolarization are not fully understood. In addition, the question that still persists is, since PKA is activated within 1 minute of exposure to a capacitating medium and coincides with the increase in sAC-derived cAMP, why does it take 30 minutes to trigger the potential change? This question extends to a series of events that, being commanded by PKA, take longer to occur, such as actin polymerization and the activation of Tyr-kinases like Src. Our group identified that PKA promotes the activation of Src, then allowing its full activation by phosphorylation of Src-Tyr416. In turn, through heterologous expression of Slo3 in Xenopus oocytes, we demonstrated that Src is essential for the sensitization of the K+ channel Slo3, responsible for Em hyperpolarization. The results of this work will aid in understanding the regulation of these events in different cell types, such as the regulation of Src in different types of cancer.
Our objective is to understand the regulation of various signaling cascades (see working model in Figure), which, although triggered by the same mechanisms, are controlled both temporally and spatially in different ways in cellular systems. Our group, made up of a network of collaborators, integrates different techniques, coupling the analysis of physiological parameters derived from single-cell studies such as flow cytometry and super-resolution microscopy, with population measurements such as suspension cell fluorimetry and mass spectrometry.
