What is the significance of IRS 1 phosphorylation in insulin signaling?

IRS 1 phosphorylation has no significant role in insulin signaling.

IRS 1 phosphorylation is crucial for activating downstream signaling pathways involved in cell growth.

IRS 1 phosphorylation inhibits downstream signaling pathways, reducing cell growth.

IRS 1 phosphorylation leads to its degradation, terminating the signal.