Phospholipase Cβ interacts with cytosolic partners to regulate cell proliferation

Abstract

Phospholipase Cβ (PLCβ) is the main effector of the Gαq signaling pathway relaying different extracellular sensory information to generate intracellular calcium signals. Besides this classic function, we have found that PLCβ plays an important but unknown role in regulating PC12 cell differentiation by interacting with components in the RNA-induced silencing machinery. In trying to understand the role of PLCβ in PC12 cell differentiation, we find that over-expressing PLCβ reduces PC12 cell proliferation while down-regulating PLCβ increases the rate of cell proliferation. However, this behavior is not seen in other cancerous cell lines. To determine the underlying mechanism, we carried out mass spectrometry analysis of PLCβ complexes in PC12 cells. We find that in unsynchronized cells, PLCβ primarily binds cyclin-dependent kinase (CDK)16 whose activity plays a key role in cell proliferation. In vitro studies show a direct association between the two proteins that result in loss in CDK16 activity. When cells are arrested in the G2/M phase, a large population of PLCβ is bound to Ago2 in a complex that contains C3PO and proteins commonly found in stress granules. Additionally, another population of PLCβ complexes with CDK18 and cyclin B1. Fluorescence lifetime imaging microscopy (FLIM) confirms cell cycle dependent associations between PLCβ and these other protein binding partners. Taken together, our studies suggest that PLCβ may play an active role in mediating interactions required to move through the cell cycle.

Stimulation of phospholipase Cβ1 by Gα q promotes the assembly of stress granule proteins

“…Studies showed that PLCβ1 can localize to the nucleus to regulate cell growth and differentiation, possibly through modulation of phosphatidylinositol 4,5-bisphosphate (PIP 2 ) abundance in the nuclear envelope ( 41 , 42 ). We previously found that a stable, cytosolic population of PLCβ1 affects various cell functions, such as RNA silencing and neuronal cell differentiation and proliferation independently of its catalytic activity ( 43 , 44 ). These alternative cytosolic functions of PLCβ only occur at specific and limited times in the cell cycle.…”

Gαq-mediated calcium dynamics and membrane tension modulate neurite plasticity

“…Additionally, the loss of neurites during retraction shifts its associated plasma membrane population to the cytosol in the cell body. This net increase in the cytosolic PLCβ population will promote PLCβ's cytosolic roles in directing translation of specific mRNAs (see Scarlata et al, 2018;Scarlata, 2019), which are typically not operative during Gαq stimulation. The net effect of cytosolic PLCβ would be shifting protein populations during longer times not probed in this study.…”

Stimulation of phospholipase Cβ1 by Gαq promotes the assembly of stress granule proteins

“…Cocco and other have shown that PLCβ1 can localize to the nucleus to regulate cell growth and differentiation (see (32,33)). Our lab has found that PLCβ1 has a stable cytosolic population that impacts various cell functions, such as RNA silencing, and neuronal cell differentiation and proliferation (34,35). These alternate cytosolic functions of PLCβ only occur at specific and limited times in the cell cycle.…”