The lab you work in has discovered a previously unidentified extracellular signal molecule called QGF, a 75,000-dalton protein. You add purified QGF to different types of cells to determine its effect on these cells. When you add QGF to heart muscle cells, you observe an increase in cell contraction. When you add it to fibroblasts, they undergo cell division. When you add it to nerve cells, they die. When you add it to glial cells, you do not see any effect on cell division or survival.

A. How can the same signaling molecule cause such diverse affects? Why do the glial cells not respond at all?

B. Devise a signaling pathway that QGF could use to increase contractions in in the heart. (Hint: Ca2+ is very important for muscle contraction)

C. Devise a signaling pathway that QGF could use to lead to apoptosis of nerve cells.

D. Devise a signaling pathway that QGF could use to induce cell division in the fibroblasts?

A- It is because said molecule presents binding to different receptors and in the case of glia cells it does not present an answer because they do not have a specific receptor for said molecule.

b-in the case of muscle, this molecule could bind to calcium channels or to the REL itself, generating the opening of said channels or the release of calcium found in REL. In this way, by increasing the intracellular concentration of calcium, it activates the actin head, causing the topoisomerase to move and promoting binding with myosin. Once the activated actin will perform a "rowing" movement to generate the drag of the myosin and the union of the Z lines.

c-In the process of neuronal apoptosis, the cell itself generates biochemical signals (either by positive induction in which the receptors and receptors of the membrane bind to certain substances, or by negative or mitochondrial induction in which the ability to suppress certain substances is lost. substances that would generate the activity of apoptotic enzymes) that cause them to condense and alter the cytoplasm, the cell membrane, the cell nucleus to collapse and DNA to fragment. Finally, the microglial cells end up phagocytizing and eliminating the remains of the dead neurons, so that they do not generate interference for the normative functioning of the brain.

d- This molecule could fulfill a path similar or similar to that of growth factors, that is how they are associated with heparan sulfate of the extracellular matrix, which serves as a warehouse for inactive factors. FCFs contribute to different types of responses, such as wound healing, hematopoiesis, angiogenesis, or embryonic development

Explanation:

Regarding the explanation, it is important to keep in mind that this molecule can play a role both in the nervous system and in other organs, that is why in case it is sought that it does not have this apoptotic effect on neurons, some coarse, macro compound that allows the blood-brain barrier to not allow passage.