Biology subjects

LaFlamme, S. E.

Publications and source records attributed to LaFlamme, S. E..

4 recordsLinked to original sources

bioRxiv2021

Laminin-binding Integrins Regulate Angiogenesis by Distinct and Overlapping Mechanisms in Organotypic Cell Culture Models

Endothelial cells engage extracellular matrix and basement membrane components through integrin-mediated adhesion to promote angiogenesis. Our previous studies demonstrated that endothelial expression of laminin-411 and laminin-511 as well as 6 integrins is required for endothelial sprouting and tube formation in organotypic angiogenesis assays. These studies demonstrated that 6 integrins promote migration and regulate the expression of ANGPT2 and CXCR4 and that 6-dependent regulation of CXCR4 contributes to endothelial morphogenesis in our assays. However, these studies did not identify specific roles for the 6{beta}1, 6{beta}4, or 3{beta}1 laminin-binding integrins. Here, we employ RNAi technology to parse the contributions of these integrins. We demonstrate that 6{beta}4 promotes migration, sprouting, and tube formation, and also positively regulates the expression of ANGPT2, but does not promote CXCR4 expression, suggesting that 6{beta}1 functions in this regulation. Additionally, we show that 3{beta}1 regulates endothelial sprouting and tube formation, but is not required for migration in our assays or for the expression of ANGPT2 or CXCR4. Integrin 3{beta}1 promotes the expression of NRP1 and ID1 RNAs, both of which are known to promote angiogenesis. Taken together, our results indicate that laminin-binding integrins play distinct roles during endothelial morphogenesis and do not compensate for one another in organotypic culture. Summary StatementThe laminin-binding integrins 3{beta}1, 6{beta}1, and 6{beta}4 contribute to endothelial sprouting and tube formation in organotypic angiogenesis assays.

cell biology↗

bioRxiv2021

The Transcriptional Co-Activator Taz Contributes to the Differentiation of a Salivary Gland Epithelial Cell Line Towards a Myoepithelial Phenotype

The salivary gland can be permanently impaired by radiation treatment for head and neck cancers. Efforts at tissue regeneration have focused on saliva-producing acinar cells. However, myoepithelial cells are also critical to gland function, but mechanisms that regulate their differentiation are poorly defined. To study myoepithelial differentiation, we employed mSG-PAC1 murine salivary gland epithelial cells. We demonstrate that mSG-PAC1 spheroids exhibit phenotypic plasticity between pro-acinar and myoepithelial cell fates. Increased expression of pro-acinar/acinar or myoepithelial RNAs was identified from spheroids cultured under different media conditions by microarray followed by gene-set enrichment analysis. Spheroids cultured with different medium components expressed proteins typical of either acinar or myoepithelial cells, as detected by immunocytochemistry. We demonstrate that the pattern of TAZ expression in the epithelial compartment of the differentiating murine salivary gland correlates with the expression of the myoepithelial marker alpha-SMA, as is the case for TAZ expression in mSG-PAC1 spheroids. Our analysis also indicates that YAP/TAZ target genes are upregulated together with myoepithelial markers. Importantly, siRNA targeting of TAZ expression in mSG-PAC1 spheroids diminished the expression of myoepithelial markers. Our results in this in vitro cell model implicate TAZ signaling in myoepithelial differentiation.

cell biology↗

bioRxiv2019

Alpha 6 Integrins Regulate the Expression of Laminin-511 and CXCR4 to Promote Endothelial Tubular Morphogenesis

During angiogenesis, endothelial cells engage components of the extracellular matrix through integrin-mediated adhesion. Endothelial expression of laminin-411 and laminin-511 are known to promote vessel stability. However, little is known about the contribution of these laminins to endothelial morphogenesis. We used two organotypic cell culture angiogenesis assays in conjunction with RNAi approaches to demonstrate that depletion of either the 4 chain of laminin-411 or the 5 chain of laminin-511 from endothelial cells inhibits sprouting and tube formation. Depletion of 6 integrins resulted in similar phenotypes. Gene expression analysis indicated that loss of either laminin-511 or 6 integrins inhibited the expression of CXCR4, a gene previously associated with angiogenic endothelial cells. Pharmacological or RNAi-dependent inhibition of CXCR4 suppressed endothelial sprouting and morphogenesis. Importantly, expression of recombinant CXCR4 rescued endothelial morphogenesis when the 6 integrin expression was inhibited. Additionally, the depletion of 6 integrins from established tubes resulted in the loss of tube integrity and laminin-511. Taken together, our results indicate that 6 integrins and laminin-511 can promote endothelial morphogenesis by regulating the expression of CXCR4 and suggest that the 6-dependent deposition of laminin-511 protects the integrity of established endothelial tubes. Summary statementEndothelial-secreted laminin-511 and 6 integrins promote endothelial morphogenesis by regulating the expression of the chemokine receptor, CXCR4. The depletion of 6 integrins from established tubes results in the loss of tube integrity and laminin-511.

cell biology↗

bioRxiv2019

Alpha 6 integrins promote cytokinesis by regulating the expression of RSK2 and MKLP1

The integrin-mediated interaction of cells with components of the extracellular matrix (ECM) regulates many cellular processes including cell division. Cytokinesis is the last step of cell division and is critical for normal development and tissue homeostasis as it ensures the proper segregation of genetic and cytoplasmic material between daughter cells. Cytokinesis failure leads to defects in development and tissue differentiation, as well as tumorigenesis. Abscission of intercellular bridge that connects presumptive daughter cells is the last step of cell division. The mitotic kinesin-like protein 1 (MKLP1) plays a central role in positioning the abscission machinery. Here, we show that 6 integrins promote successful cytokinesis in salivary gland epithelial cells by regulating the expression of MKLP1. RNAi-mediated depletion of 6 integrins inhibits cytokinesis and the expression of MKLP1 and p90 ribosomal-S6-kinase 2 (RSK2). Depletion of RSK2 results in similar defects in cytokinesis and also inhibits the expression of MKLP1, suggesting that the expression of RSK2 is required downstream of integrins to promote MKLP1 expression and successful cytokinesis. RNAi-mediated depletion of RSK2 in embryonic salivary glands in organ culture also results in the inhibition of cytokinesis and MKLP1 expression, indicating the physiological significance of this pathway.

cell biology↗