This set of Molecular Endocrinology Multiple Choice Questions & Answers (MCQs) focuses on “Receptors that Signal through Associated Tyrosine Kinases – Set 2”.
1. Mutation in, which among the following Janus Kinases is linked to combined immunodeficiency diseases?
a) JAK3
b) JAK2
c) JAK7
d) JAK8
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Explanation: JAKs seem to be essential to proper human functioning. An autosomal recessive type of extreme combination immunodeficiency disease has been related to mutations in the JAK3 gene. This gene has its major role regulating the immune functions of our body.
2. Which is the one family of signaling proteins appears to be particularly important for the function of cytokines?
a) CLB
b) STATs
c) Interferon Gamma
d) Leptopterone
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Explanation: The signalling proteins recruited to cytokine receptor-JAK complex subsets are normally the same as those recruited to tyrosine kinases of the receptor. However, it seems that one class of signalling proteins is especially essential for the role of cytokines and they are signal transducers and transcription activators.
3. Which type of STAT is present in receptor for leukemia inhibitory factor?
a) STAT7
b) STAT1
c) STAT3
d) STAT5
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Explanation: There are seven STAT3 binding motifs in the receptor for leukemia inhibitory factor (YxxQ, of which Y is tyrosine, Q is glutamine, and x can be any amino acid). And this receptor is an especially potent activator of STAT3.
4. STAT proteins are latent factors of cytoplasmic transcription that cycle between the nucleus and the cytoplasm.
a) True
b) False
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Explanation: STAT proteins are latent factors of cytoplasmic transcription that cycle between the nucleus and the cytoplasm. Inactive STATs in the cytoplasm bind by their SH2 domains to one or more phosphorylated tyrosines in activated receptor-JAK complexes.
5. The transcriptional activity of STAT5 is diminished when it forms a complex with the estrogen receptor.
a) True
b) False
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Explanation: While forming a complex with glucocorticoid, mineralocorticoid, and progesterone receptors, the transcriptional function of STAT5 is increased. However, when it forms a complex with the estrogen receptor, the transcriptional activity is reduced.
6. The severe growth failure in humans is associated with point mutations in which among the following STATs?
a) STAT5A
b) STAT5B
c) STAT7B
d) STAT7A
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Explanation: The value of STAT5B for GH signalling is demonstrated by the discovery that point mutations in the STAT5B gene are associated with serious growth failure in humans. This results in an unstable, truncated form of STAT5B, or a dysfunctional SH2 domain.
7. In which among the following JAKs is the point mutation seen in the case of myeloproliferative disorder?
a) JAK2
b) JAK8
c) JAK1
d) JAK3
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Explanation: JAKs and STATs that are constitutively activated are consistent with cellular transformation. For instance, in most patients with a myeloproliferative disease, a single acquired activating point mutation in JAK2 is present.
8. Which among the following fusion proteins is constitutively active in leukemia?
a) TEL-JAK7
b) TEL-JAK5
c) SEL-JAK5
d) TEL-JAK2
View Answer
Explanation: A typical feature of leukemias are constitutively active JAKs and STATs, and JAK2 and STAT5B have been recognized as fusion partners in leukemia translocations. The fusion protein TEL-JAK2 is constitutively active, leading to STAT proteins that are again constitutively active.
9. Which proteins are important players in the termination or suppression of cytokine signaling pathways?
a) SOCS
b) TEL-JAK2
c) CBL-JAK7
d) CABL
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Explanation: The suppressors of cytokine-signaling (SOCS) protein suppressors are known to be especially important participants in the termination or repression of cytokine signalling pathways. Proteins from SOCS are an exceptional example of an important negative feedback loop.
10. Which SOCS protein is thought to bind to phosphotyrosines in the kinase domain of JAK?
a) SOCS3
b) SOCS1
c) SOCS2
d) SCOS7
View Answer
Explanation: SOCS proteins are known to bind to phosphotyrosines in the kinase domain of JAK in some cases, as in SOCS 1. This is able to suppress the operation of kinase which has the phosphorylation abilities.
Sanfoundry Global Education & Learning Series – Molecular Endocrinology.
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