nbme q on acromegaly

[sadaca]

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Hey guys, I am confused on this, I was reading more into online and courses say, if its a pitutary adenoma(Which this q states, then its high GH) and sometimes it can be nonpituitary due to high GHRH. Also this question states SOMATOTROPHS which are pituitary cells secreting GH.
Can someone plz help with this? ANS: A

35 y/o man with 3 yr history of enlarging nose, coarse facies, muscle weakness, increased hand/foot size. Large fleshy nose and prognathism on exam. High IGF-1 in serum. MRI shows pituitary adenoma. Morphologic analysis of the tumor shows a densely granulated somatotroph adenoma. Further studies show that the G alpha-s subunit of the tumor G proteins lack GTPase activity.

The tumor cells most likely have an increased activity of which enzyme?

Adenylyl cyclase
Guanylyl cyclase
Janus kinase
Phospholipase C
Tyrosine kinase

 

[notbobtrustme]

Hey guys, I am confused on this, I was reading more into online and courses say, if its a pitutary adenoma(Which this q states, then its high GH) and sometimes it can be nonpituitary due to high GHRH. Also this question states SOMATOTROPHS which are pituitary cells secreting GH.
Can someone plz help with this? ANS: A

35 y/o man with 3 yr history of enlarging nose, coarse facies, muscle weakness, increased hand/foot size. Large fleshy nose and prognathism on exam. High IGF-1 in serum. MRI shows pituitary adenoma. Morphologic analysis of the tumor shows a densely granulated somatotroph adenoma. Further studies show that the G alpha-s subunit of the tumor G proteins lack GTPase activity.

The tumor cells most likely have an increased activity of which enzyme?

Adenylyl cyclase
Guanylyl cyclase
Janus kinase
Phospholipase C
Tyrosine kinase

Gas -> always on because lack of GTPase activity, hence, can't turn off and activates AC.

 

[sadaca]

Thanks alot .
wow, the question gives it away eh? Gs is cAMP.
But you say lack of GTPase, however that is the RAS MAP kinase(via tyrosine kinase) is GTP mediated?

 

[dyspareunia]

Thanks alot .
wow, the question gives it away eh? Gs is cAMP.
But you say lack of GTPase, however that is the RAS MAP kinase(via tyrosine kinase) is GTP mediated?

What does RAS MAP have to do with it? Without GTPase, the G protein is never inactivated because GTP is always bound.

 

[notbobtrustme]

Thanks alot .
wow, the question gives it away eh? Gs is cAMP.
But you say lack of GTPase, however that is the RAS MAP kinase(via tyrosine kinase) is GTP mediated?

sure, maybe, I dunno, I'd have to see the question regarding that.

However, in this case, it's the piturary adenoma that's secreting GH. In this case, the pathway to synthesize and secrete GH is signaled by a G protein. That's why, when always active, GH is being secreted. GH works on tyrosine kinase receptors and all that jazz, but that's not in the scope of this question. It's basically asking what is the signal to secrete GH, which is G-protein mediated. In this case, an inhibitor is broken, making the system autonomous.

 

[sadaca]

@notbobtrustme thank you so much for the breakdown of this q

 

[Azurophil]

This is not a question on acromegaly.. it's really just a question on GPCR mech of action.