Although the function of ICAM5 in the pituitary is unknown, its roles in the brain as a cell adhesion molecule have been extensively studied. ICAM5 is abundantly expressed in the dendritic filopodia and plays an important role in synapse formation with presynaptic axons, via the extracellular matrix molecule, vitronectin (63), and/or β1 integrins (32, 64). Once these connections are established, the extracellular domain of ICAM5 is cleaved, disrupting the cytoplasmic actin cytoskeleton through to α-actinin or ERM (ezrin/radixin/moesin) proteins promoting reorganization to induce spine maturation (31-34, 34, 65, 66). Based on the role of ICAM5 in cell adhesion and its ability to alter the actin cytoskeleton, we propose that ICAM5 may play a role in structural organization of functional homotypic cell networks within the pituitary.
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Cells and cell networks can also adjust in response to external stimuli. For example, GnRH signaling in gonadotrope cells can cause actin reorganization, resulting in membrane projections and cellular migration towards blood vessels (70). Interestingly, pituitary cell networks can also exhibit sex differences. For example, a higher proportion of somatotrope cells respond to growth hormone releasing hormone (GHRH) in males than in females (71). It is possible that something similar may be happening with the gonadotrope population due to expression of ICAM5. Also, cell networks can be regulated by hormonal mechanisms because gonadectomy alters the responsiveness of cells to GHRH, including hormone release and cell motility (71, 72). In gonadotropes, GnRH treatment leads to an increase in process extension, which is enhanced by prior E2 exposure (73). Therefore, it is evident that sex differences can exist in pituitary networks and these networks can be regulated by gonadal
Cells and cell networks can also adjust in response to external stimuli. For example, GnRH signaling in gonadotrope cells can cause actin reorganization, resulting in membrane projections and cellular migration towards blood vessels (70). Interestingly, pituitary cell networks can also exhibit sex differences. For example, a higher proportion of somatotrope cells respond to growth hormone releasing hormone (GHRH) in males than in females (71). It is possible that something similar may be happening with the gonadotrope population due to expression of ICAM5. Also, cell networks can be regulated by hormonal mechanisms because gonadectomy alters the responsiveness of cells to GHRH, including hormone release and cell motility (71, 72). In gonadotropes, GnRH treatment leads to an increase in process extension, which is enhanced by prior E2 exposure (73). Therefore, it is evident that sex differences can exist in pituitary networks and these networks can be regulated by gonadal