A cell expresses a transmembrane protein that is cleaved at the plasma membrane

Question

A cell expresses a transmembrane protein that is cleaved at the plasma membrane to release an extracellular fragment. The fragment binds to receptor proteins on nearby cells and activates signaling pathways resulting in altered gene expression patterns in the cells. What form of intercellular signaling does this represent? Contact-dependent signaling Paracrine signaling Endocrine signaling Synaptic signaling If cells that have started mitosis were treated with nocodazole, a drug that depolymerizes microtubules, what would happen? Where would you expect Mad2 protein to be localized? The cells arrest in prometaphase:Mad2 is localized to the spindle poles The cells arrest in telophase:Mad2 is localized to the spindle poles The cells arrest in prometaphase:Mad2 is localized to almost all kinetochores The cells arrest in telophase:Mad2 is localized to almost all kinetochores If this protein is unable to hydrolyze its bound GTP, invaginated clathrin-coated pits accumulate but fail to pinch off from the plasma membrane. In neurons, long vesicle necks collared by the protein are observed and presynaptic endocytosis is blocked. This protein... contains a PI(4, 5)P_2 binding domain and a GTPase domain may change the membrane lipid composition by recruiting lipid-modfying enzymes may directly distort the membrane using the energy from GTP hydrolysis All of the above All cells in a multicellular organism have normally developed from a single cell and share the same genome, but can nevertheless be wildly different in their shape and function. What in the eukaryotic genome is responsible for this cell-type diversity? The genes that encode transcription regulatory proteins The regulatory sequences that control the expression of genes The genes that code for molecules involved in receiving cellular signals All of the above

Explanation / Answer

Q. 1 Paracrine Signaling is the type of signaling that is characterized by the production of a signal which in turn induces the behavior of these cells. As in the question, the signaling caused a change in the genetic expressions patterns, thus the signaling is Paracrine signaling. It cannot be Contact-dependent signaling since the cells in question are not in contact. For it to be Synaptic signaling, a synapse needs to be present, which is not there, in this case. Endocrine Signaling involves the secretion of hormones as compared to Paracrine Signaling, wherein part of the cell is detached.

Q. 2 Since the cell is treated with nocodazole, the cell is prevented from making metaphase spindles, because microtubules do not polymerise. So cells enter mitosis, however get arrested in the prometaphase. Also, the MAD2 proteins are seen attached to the kinetochores.

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